Search

It is unknown whether generalized vascular dysfunction precedes the development of kidney disease. Therefore, we studied myogenic constriction and endothelium-mediated dilatory responses in two inbred Fawn-Hooded (FH) rat strains, one of which spontaneously develops hypertension, proteinuria, and glomerulosclerosis (FHH), whereas the other (FHL) does not. Small renal, mesenteric resistance arteries and thoracic aorta isolated from FH rats before (7 wk old) and after the development of mild proteinuria (12 wks old) were mounted in perfused and isometric set-ups, respectively. Myogenic response, endothelium-dependent relaxation, and the contribution of endothelium-mediated dilatory compounds were studied using their respective inhibitors. Myogenic reactivity was assessed constructing pressure-diameter curves in the presence and absence of calcium. At the age of 7 wk, renal arteries isolated from kidneys of FHH rats developed significantly lower myogenic tone compared with FHL, most likely because of excessive cyclo-oxygenase 1-mediated production of constrictive prostaglandins. Consequently, young FHH demonstrated reduced maximal myogenic tone (22 [+ or -] 4.8 vs. 10.8 [+ or -] 2.0%, P = 0.03) and the peak myogenic index (-6.9 [+ or -] 4.8 vs. 0.6 [+ or -] 0.8%/mmHg, P = 0.07 for FHL vs. FHH, respectively). Active myogenic curves obtained in mesenteric arteries isolated from 7-wk-old rats did not differ between either strain, demonstrating a similar level of systemic myogenic tone in FHL and FHH rats. Therefore, before any renal end-organ damage is present, myogenic response seems selectively impaired in renal vasculature of FHH rats. Aortic reactivity did not differ between FHL and FHH at the time points studied. The present study shows that vascular dysfunction in both small renal and systemic arteries precedes renal end-organ damage in a spontaneous model of hypertension-associated renal damage. These early vascular changes might be potentially involved in the increased susceptibility of FHH rats to renal injury. myogenic response; endothelial dysfunction; Fawn-Hooded rat; chronic kidney disease; hypertension; nitric oxide; endothelium-derived hyperpolarizing factor; prostaglandins doi:10.1152/ajprenal.00289.2009

The obese Zucker rat reportedly has increased activity of the intrarenal renin-angiotensin-aldosterone system, which conceptually could contribute to elevated salt sensitivity and blood pressure (BP). Our aim was to determine whether there was increased angiotensin II type 1 receptor (A[T.sub.1]R)-mediated upregulation of expression or activity of the bumetanide-sensitive Na-K-2Cl cotransporter, the thiazide-sensitive Na-Cl cotransporter (NCC), and/or the epithelial sodium channel (ENaC) in obese vs. lean Zucker rats. Male obese and lean Zucker rats (10-wk old) were fed either 1) control chow (1% NaC1) or 2) chow with candesartan (CAN), an A[T.sub.1]R antagonist (25 mg/kg*diet) for 14 wk (n = 8/treatment/body type). BP measured by radiotelemetry, was markedly reduced by CAN (~20-25 mmHg) in both lean and obese rats with no body-type differences. Obese rats had significantly greater net natriuretic response to single injections of hydrocblorothiazide and benzamil, suggesting increased activity of NCC and ENaC, respectively; however, only the response to benzamil was reduced by CAN. CAN led to a significant reduction in whole kidney levels of NCC and [gamma]-ENaC (70-kDa band) in both lean and obese rats. However, it significantly increased [alpha]-ENaC and Na-K-2Cl cotransporter levels, and these increases were greater in obese rats. These studies suggest that relatively increased ENaC, but not NCC activity, in obese rats is due to enhanced A[T.sub.1]R activity. CAN attenuated the reduction of several renal transporters in the obese rat kidney. Finally, differences in intrarenal A[T.sub.1]R activity do not seem directly responsible for BP differences between lean and obese rats. insulin resistance; type 2 diabetes; thiazide-sensitive Na-Cl cotransporter; bumetanide-sensitive Na-K-2Cl cotransporter

Peritoneal fibrosis (PF) is an important complication of long-term peritoneal dialysis. Although mineralocorticoid and mineralocorticoid receptor (MR) have attracted increasing attention in the field of vascular injury, including the heart, kidney, and vessels, little is known about the role of mineralocorticoid in PF. This work was designed to explore the effects of MR blockade on PF. We developed a new model of PF in rats based on mechanical scraping of the peritoneum. This model is characterized by acute-phase inflammation (neutrophil and macrophage infiltration on days 0-3) and late-phase PF ([alpha]-smooth muscle actin-positive fibroblast infiltration, type III collagen accumulation, and neoangiogenesis on days 7-14). Peritoneal thickening peaked on day 14. MR was expressed in rat peritoneum and a rat fibroblast cell line. Expression of its effector kinase [serum- and glucocorticoid-induced kinase-1 (Sgk1)], transforming growth factor-[beta] (TGF-[beta]), plasminogen activator inhibitor-1 (PAI-1), and CD31-positive vessels increased during the course of PF. Rats were treated with spironolactone, angiotensin receptor blockade (ARB), or angiotensin-converting enzyme inhibitor (ACEI)-ARB-spironolactone starting at 6 h after peritoneal scraping. All parameters, including peritoneal thickening, number of macrophages and CD31-positive vessels, and expression of monocyte chemoattractant protein-l, TGF[beta] PAI-1, and Sgk1, were significantly suppressed by spironolactone (10 mg*[kg.sup.-1]*[day.sup.-1]). The effects of spironolactone (10 and 20 mg*[kg.sup.-1]*[day.sup.-1]) were very similar to those of triple blockade. ARB, but not ACEI, significantly reduced peritoneal thickening. Furthermore, peritoneal function assessed by peritoneal equilibration test was significantly improved by spironolactone. Our results suggest that MR is a potential target to prevent inflammation-induced PF in patients on peritoneal dialysis. serum- and glucocorticoid-induced kinase-1; renin-angiotensin-aldosterone system; ultrafiltration failure; neoangiogenesis

It has been assumed that the pathogenesis of hydrocephalus includes a cerebrospinal fluid (CSF) absorption deficit. Because a significant portion of CSF absorption occurs into extracranial lymphatics located in the olfactory turbinates, the purpose of this study was to determine whether CSF transport was compromised at this location in a kaolin-induced communicating (extraventricular) hydrocephalus model in rats. Under 1-3% halothane anesthesia, kaolin (n = 10) or saline (n = 9) was introduced into the basal cisterns of Sprague-Dawley rats, and the development of hydrocephalus was assessed 1 wk later using MRI. After injection of human serum albumin ([sup.125]I-HSA) into a lateral ventricle, the tracer enrichment in the olfactory turbinates 30 min postinjection provided an estimate of CSF transport through the cribriform plate into nasal lymphatics. Lateral ventricular volumes in the kaolin group (0.073 [+ or -] 0.014 ml) were significantly greater than those in the saline-injected animals (0.016 [+ or -] 0.001 ml; P = 0.0014). The CSF tracer enrichment in the olfactory turbinates (expressed as percent injected/g tissue) in the kaolin rats averaged 0.99 [+ or -] 0.39 and was significantly lower than that measured in the saline controls (5.86 [+ or -] 0.32; P < 0.00001). The largest degree of ventriculomegaly was associated with the lowest levels of lymphatic CSF uptake with lateral ventricular expansion occurring only when almost all of the lymphatic CSF transport capacity had been compromised. We conclude that lymphatic CSF absorption is impaired in a kaolin-communicating hydrocephalus model and that the degree of this impediment may contribute to the severity of the induced disease. extraventricular hydrocephalus; ventriculomegaly; cribriform plate; olfactory turbinates; arachnoid villi and granulations; lymph; intracranial pressure

Previously, we presented in vivo evidence for a physiological significance of cAMPregulated CFTR [C1.sup.-] channels in [Ca.sup.2+]-activated [C1.sub.-] reabsorption in the ductal system of the rat submandibular gland. Here, we address the mechanism by which basal CFTR activation contributes to the transepithelial [Cl.sub.-] movement evoked by muscarinic stimulation. The [C1.sub.-1] concentration ([[C1.sub.-]]) was increased in the final saliva from rat submandibular gland during pilocarpine stimulation when a small interfering RNA for CFTR or a specific CFTR inhibitor, [CFTR.sub.inh]172, was injected retrogradely into the gland's own duct, indicating that basal CFTR activation is involved in [C1.sub.-] reabsorption. Systemically administered propranolol failed to alter the [CI ], suggesting little involvement of a [beta]-adrenergic pathway in the C1 movement that occurs through basal CFTR activation. Intraductal injection of suramin (a nonspecific P2-receptor antagonist) increased the salivary [[C1.sup.-]], indicating the existence of endogenous purinergic activation. Upon separate intraductal injection, ATP and a P2[Y.sub.2]-receptor agonist, UTP, decreased the salivary [[C1.sup.-1]] almost equipotently. CFT[R.sub.inh]-172 and suramin each prevented these effects, whereas 2',3'-O-(4-benzoylbenzoyl)-ATP (Bz-ATP), a P2X7 agonist, had no specific effect. Pilocarpine stimulation evoked ATP secretion into the salivary fluid. Immunohistochemistry revealed the partial coexistence of CFTR and P2[Y.sup.2] receptors on the luminal surface of epithelial cells in the striated ducts of this gland. These results raise the possibility that muscarinic stimulation-induced [C1.sup.-] reabsorption occurs through basal CFTR activity and that this is regulated by P2[Y.sub.2] receptors in the ductal epithelium via stimulation by ATP secreted into the salivary fluid. salivary; duct; reabsorption; P2[Y.sub.2] receptor: cystic fibrosis transmembrane conductance regulator

Approximately one-third of patients with stress urinary incontinence (SUI) also suffer from urgency incontinence, which is one of the major symptoms of overactive bladder (OAB) syndrome. Pudendal nerve injury has been recognized as a possible cause for both SUI and OAB. Therefore, we investigated the effects of pudendal nerve ligation (PNL) on bladder function and urinary continence in female Sprague-Dawley rats. Conscious cystometry with or without capsaicin pretreatment (125 mg/kg sc), leak point pressures (LPPs), contractile responses of bladder muscle strips to carbachol or phenylephrine, and levels of nerve growth factor (NGF) protein and mRNA in the bladder were compared in sham and PNL rats 4 wk after the injury. Urinary frequency detected by a reduction in intercontraction intervals and voided volume was observed in PNL rats compared with sham rats, but it was not seen in PNL rats with capsaicin pretreatment that desensitizes C-fiber-afferent pathways. LPPs in PNL rats were significantly decreased compared with sham rats. The contractile responses of detrusor muscle strips to phenylephrine, but not to carbachol, were significantly increased in PNL rats. The levels of NGF protein and mRNA in the bladder of PNL rats were significantly increased compared with sham rats. These results suggest that pudendal nerve neuropathy induced by PNL may be one of the potential risk factors for OAB, as well as SUI. Somato-visceral cross sensitization between somatic (pudendal) and visceral (bladder) sensory pathways that increases NGF expression and [[alpha].sub.1]-adrenoceptor-mediated contractility in the bladder may be involved in this pathophysiological mechanism. nerve growth factor; cross-talk sensitization; [[alpha].sub.1]-adrenoceptor; capsaicin

This study was designed to test the hypothesis that the transient receptor potential vanilloid type 1 (TRPV1) channel, expressed primarily in sensory nerves, and substance P (SP), released by sensory nerves, play a protective role against lipopolysaccharide (LPS)-induced hypotension. LPS (10 mg/kg iv) elicited tachycardia and hypotension in anesthetized male Wistar rats, which peaked at 10 min and gradually recovered 1 h after the injection. Blockade of TRPV1 with its selective antagonist capsazepine (CAPZ, 3 mg/kg iv) impaired recovery given that the fall in mean arterial pressure (MAP) was greater 1 h after CAPZ plus LPS injections compared with LPS injection alone (45 [+ or -] 5 vs. 25 [+ or -] 4 mmHg, P < 0.05). Blockade of the neurokinin 1 (NK1) receptor with its selective antagonists RP-67580 (5 mg/kg iv) or L-733,060 (4 mg/kg iv) prevented recovery, considering that falls in MAP were not different 1 h after injections of NKI antagonists plus LPS from their peak decreases (66 [+ or -] 9 vs. 74 [+ or -] 5 mmHg or 60 [+ or -] 7 vs. 69 [+ or -] 3 mmHg, respectively, P > 0.05). LPS increased plasma SP, norepinephrine (NE), and epinephrine (Epi) levels compared with vehicles, and the increases in plasma SP, NE, and Epi were significantly inhibited by CAPZ or RP-67580. The survival rate at 24 or 48 h after LPS injection (20 mg/kg ip) was lower in conscious rats pre-treated with CAPZ or RP-67580 compared with rats treated with LPS alone (P < 0.05). Thus our results show that the TRPV1, possibly via triggering release of SP which activates the NK1 and stimulates the sympathetic axis, plays a protective role against endotoxin-induced hypotension and mortality, suggesting that TRPV1 receptors are essential in protecting vital organ perfusion and survival during the endotoxic condition. endotoxin; transient receptor potential vanilloid type 1 channel; substance

In hypothyroid patients, altered microvascular structure and function may affect mood and cognitive function. We hypothesized that adult male hypothyroid rats will have significantly lower forebrain blood vessel densities (BVD) than euthyroid rats and that treatment with 3,5-diiothyroprionic acid (DITPA) (a thyroid hormone analog) or thyroxine ([T.sub.4]) will normalize BVDs. The euthyroid group received no thyroidectomy or treatment. The other three groups received thyroidectomies and pellets. The hypothyroid group received a placebo pellet, the DITPA group received an 80-mg DITPA-containing pellet, and the [T.sub.4] group received a 5.2-mg [T.sub.4] slow-release pellet for 6 wk. Body weights, cardiac function, and body temperatures were measured. A monoclonal antiplatelet endothelial cell adhesion anti-body was used to visualize blood vessels. The euthyroid group averaged body weights of 548 [+ or -] 54 g, while the hypothyroid group averaged a body weight of 332 [+ or -] 19 g (P value < 0.001). Relative to the euthyroid group, the DITPA-treated group was significantly lighter (P value < 0.05), while the [T.sub.4]-treated group was comparable in body weight to the euthyroid group. The same trends were seen with body temperature and cardiac function with the largest difference between the euthyroid and hypothyroid groups. BVD in the euthyroid group was 147 [+ or -] 12 blood vessels/[mm.sup.2] and in hypothyroid group 69 [+ or -] 5 blood vessels/[mm.sup.2] (P = 0.013) but similar among the euthyroid, DITPA, and [T.sub.4] groups. These results show that hypothyroidism decreased BVD in adult rat forebrain regions. Moreover, DITPA and [T.sub.4] were efficacious in preventing effects of hypothyroidism on cardiac function and BVD. hypothyroid; angiogenesis; echocardiography; thyroid hormones

This study examined the impact of age on contractile function, [Ca.sup.2+] homeostasis, and cell viability in isolated myocytes exposed to simulated ischemia and reperfusion. Ventricular myocytes were isolated from anesthetized young adult (3 too) and aged (24 too) male Fischer 344 rats. Cells were fieldstimulated at 4 Hz (37[degrees]C), exposed to simulated ischemia, and reperfused with Tyrode solution. Cell shortening and intracellular [Ca.sup.2+] were measured simultaneously with an edge detector and fura-2. Cell viability was assessed by Trypan blue exclusion. Ischemia (20-45 min) depressed amplitudes of contraction equally in isolated myocytes from young adult and aged animals. The degree of postischemic contractile depression (stunning) was comparable in both groups. [Ca.sup.2+] transient amplitudes were depressed in early reperfusion in young adult and aged cells and then recovered to preischemic levels in both groups. Cell viability also declined equally in reperfusion in both groups. In short, some cellular responses to simulated ischemia and reperfusion were similar in both groups. Even so, aged myocytes exhibited a much greater and more prolonged accumulation of diastolic [Ca.sup.2+] in ischemia and in early reperfusion compared with myocytes from younger animals. In addition, the degree of mechanical alternans in ischemia increased significantly with age. The observation that there is an age-related increase in accumulation of diastolic [Ca.sup.2+] in ischemia and early reperfusion may account for the increased sensitivity to ischemia and reperfusion injury in the aging heart. The occurrence of mechanical alternans in ischemia may contribute to contractile dysfunction in ischemia in the aging heart. calcium transients; cell shortening; senescence

We studied the origins of ectopic beats during low-flow reperfusion after acute regional ischemia in excised rat hearts. The left anterior descending coronary artery was cannulated. Perfusate was delivered to the cannula using an highperformance liquid chromatography pump. This provided not only precise control of flow rate but also avoided mechanical artifacts associated with vessel occlusion and deocclusion. Optical mapping of epicardial transmembrane potential served to identify activation wavefronts. Imaging of NADH fluorescence was used to quantify local ischemia. Our experiments suggest that low-flow reperfusion of ischemic myocardium leads to a highly heterogeneous ischemic substrate and that the degree of ischemia between adjacent patches of tissue changes in time. In contrast to transient ectopic activity observed during full-flow reperfusion, persistent ectopic arrhythmias were observed during low-flow reperfusion. The origins of ectopic beats were traceable to areas of high spatial gradients of changes in NADH fluorescence caused by low-flow reperfusion.

Statins have been shown to be cardioprotective; however, their interaction with endogenous cardioprotection by ischemic preconditioning and postconditioning is not known. In the present study, we examined if acute and chronic administration of the 3-hydroxy-3-methylglutaryl CoA reductase inhibitor lovastatin affected the infarct size-limiting effect of ischemic preconditioning and postconditioning in rat hearts. Wistar rats were randomly assigned to the following three groups: 1) vehicle (1% methylcellulose per os for 12 days), 2) chronic lovastatin (15 mg.[kg.sup.-1].[day.sup.-1] per os for 12 days), and 3) acute lovastatin (1% methylcellulose per os for 12 days and 50 [micro]mol/1 lovastatin in the perfusate). Hearts isolated from the three groups were either subjected to a nonconditioning (aerobic perfusion followed by 30-min coronary occlusion and 120-min reperfusion, i.e., test ischemia-reperfusion), preconditioning (three intermittent periods of 5-min ischemia-reperfusion cycles before test ischemia-reperfusion), or postconditioning (six cycles of 10-s ischemia-reperfusion after test ischemia) perfusion protocol. Preconditioning and postconditioning significantly decreased infarct size in vehicle-treated hearts. However, preconditioning failed to decrease infarct size in acute lovastatin-treated hearts, but the effect of postconditioning remained unchanged. Chronic lovastatin treatment abolished postconditioning but not preconditioning; however, it decreased infarct size in the nonconditioned group. Myocardial levels of coenzyme Q9 were decreased in both acute and chronic lovastatin-treated rats. Western blot analysis revealed that both acute and chronic lovastatin treatment attenuated the phoshorylation of Akt; however, acute but not chronic lovastatin treatment increased the phosphorylation of p42 MAPK/ERK. We conclude that, although lovastatin may lead to cardioprotection, it interferes with the mechanisms of cardiac adaptation to ischemic stress. coronary occlusion; coenzyme Q9; Akt; p42 mitogen-activated protein kinase/extracellular signal-regulated kinase; statin

We confirmed that release of 20-hydroxyeicosatetraenoic acid (20-HETE) from the isolated perfused kidney of diabetic rats is greatly reduced compared with age-matched control rats. The present studies were undertaken to examine potential mechanisms for the deficit in renal 20-HETE in rats with streptozotocin-induced diabetes of 3-4 wk duration. A role for oxidative stress was excluded, inasmuch as treatment of diabetic rats with tempol, an SOD mimetic, for 4 wk did not affect the renal release of 20-HETE. Similarly, chronic inhibition of nitric oxide formation with nitro-L-arginine methyl ester or aldose reductase with zopolrestat failed to alter the release of 20-HETE from the diabetic rat kidney. Inasmuch as 20-HETE may be metabolized by cyclooxygenase (COX), the expression/activity of which is increased in diabetes, we included indomethacin in the perfusate of the isolated kidney to inhibit COX but found no effect on 20-HETE release. Diabetic rats were treated for 3 wk with fenofibrate to increase expression of cytochrome P-450 (CYP4A) in an attempt to find an intervention that would restore release of 20-HETE from the diabetic rat kidney. However, fenofibrate reduced 20-HETE release in diabetic and control rat kidneys but increased expression of CYP4A. Only insulin treatment of diabetic rats for 2 wk to reverse the hyperglycemia and maintain blood glucose levels at streptozotocin diabetes; insulin; fenofibrate

Postangioplasty and in-stent restenosis remain ominous problems in percutaneous coronary intervention where good animal models of restenosis proneness and resistance are needed. We accidentally discovered that the carotid arteries (CAs) of the Harlan and Sasco substrains of Sprague-Dawley rats display drastically different restenosis phenotypes following balloon-induced endothelial denudation. When subjected to balloon injury, Sasco CAs exhibited significantly larger neointimal mass than did Harlan CAs at both days 14 and 32, as evidenced by a higher intima-to-media ratio and a greater number of intimal cells in Sasco CAs. This was due to a greater cell proliferation and to a less vigorous apoptosis of Sasco neointima, as assessed by 5-bromo-2'-deoxyuridine and terminal deoxynucleotidyl transferase-deoxyuridine nick-end labeling staining, respectively. At a cellular level, whereas vascular smooth muscle cells (VSMCs) isolated from Sasco and Harlan CAs were identical in morphology and in propensity to migrate, Sasco VSMCs proliferated more robustly and died far less, suggesting that under the exact same microenvironment, Sasco and Harlan VSMCs respond to growth and noxious stimuli in a drastically different fashion and that Sasco's significantly more robust neointimal proliferation after vascular injury in vivo can be accounted for by these intrinsic differences in VSMCs of these substrains in vitro. Sasco and Harlan Sprague-Dawley rats as well as VSMCs from these rats will prove to be powerful tools to study genes involved in the pathogenesis of restenosis. Harlan rats; Sasco rats; carotid artery injury; vascular smooth muscle cells; terminal deoxynucleotidyl transferase-deoxyuridine nick-end labeling; 5-bromo-2'-deoxyuridine

This study analyzed the oxidant generation during ischemia-reperfusion protocols of Langendorff-perfused rat hearts, preconditioned with a mitochondrial ATP-sensitive potassium channel (mitoKATp) opener (i.e., diazoxide). The autofluorescence of mitochondrial flavoproteins, and that of the total NAD(P)H pool on the one hand and the fluorescence of dyes sensitive to [H.sub.2][O.sub.2] or [O.sub.2] - [i.e., the dihydrodichlorofluoroscein ([H.sub.2]DCF) and dihydroethidine (DHE), respectively] on the other, were noninvasively measured at the surface of the left ventricular wall by means of optic fibers. Isolated perfused rat hearts were subjected to an ischemia-reperfusion protocol. Opening mitOKATP with diazoxide (100 [micro]M) 1) improved the recovery of the rate-pressure product after reperfusion (72 [+ or -] 2 vs. 16.8 [+ or -] 2.5% of baseline value in control group, P < 0.01), and 2) attenuated the oxidant generation during both ischemic (-46 [+ or -] 5% [H.sub.2]DCF oxidation and -40 [+ or -] 3% DHE oxidation vs. control group, P < 0.01) and reperfusion (-26 [+ or -] 2% [H.sub.2]DCF oxidation and -23 [+ or -] 2% DHE oxidation vs. control group, P < 0.01) periods. All of these effects were abolished by coperfusion of 5-hydroxydecanoic acid (500 [micro]M), a mito[K.sub.ATP] blocker. During the preconditioning phase, diazoxide induced a transient, reversible, and 5-hydroxydecanoic acid-sensitive flavoprotein and [H.sub.2]DCF (but not DHE) oxidation. In conclusion, the diazoxide-mediated cardioprotection is supported by a moderate [H.sub.2] [O.sub.2] production during the preconditioning phase and a strong decrease in oxidant generation during the subsequent ischemic and reperfusion phases. cardioprotection; 5-hydroxydecanoate

Clinical trials revealed that estrogen may result in cardiovascular risk in patients with coronary heart disease, despite earlier studies demonstrating that estrogen provided cardiovascular protection. It is possible that the preexisting condition of hypertension and the ability of estrogen to activate the renin-angiotensin system could confound its beneficial effects. Our hypothesis is that the attenuation of estrogen to agonist-induced vasoconstrictor responses through the activation of nitric oxide (NO) synthase (NOS) is impaired by hypertension. We investigated the effects of 17[beta]-estradiol ([E.sub.2]) replacement in normotensive Sprague-Dawley (SD) and (mRen2)27 hypertensive transgenic (TG) rats on contractile responses to three vasoconstrictors, angiotensin II (ANG II), serotonin (5-HT), and phenylephrine (PE), and on the modulatory role of vascular NO to these responses. The aorta was isolated from ovariectomized SD and TG rats treated chronically with 5 mg [E.sub.2] or placebo (P). The isometric tension of the aortic rings was measured in organ chambers, and endothelial NOS (eNOS) in the rat aorta was detected using Western blot analysis. [E.sub.2] treatment increased eNOS expression in the SD and TG aorta and reduced ANG II- and 5-HT- but not PE-induced contractions in SD and TG rats. The inhibition of NOS with [N.sup.[omega]]-nitro-L-arginine methyl ester enhanced ANG II-, 5-HT-, and PE-induced contractions in P-treated and ANG II and PE responses in [E.sub.2]-treated SD and TG rats. Only the responses to 5-HT were augmented in hypertensive rats. In conclusion, this study shows that the preexisting condition of hypertension augmented the vascular responsiveness of 5-HT, whereas the attenuation of estrogen by ANG II and 5-HT vascular responses was not impaired by hypertension. The adrenergic agonist was unresponsive to estrogen treatment. The contribution of NO as a factor contributing to the relative refractoriness of the vascular responses is dependent on the nature of the vasoconstrictor and/or the presence of estrogen. angiotensin II; serotonin; phenylephrine

Hyperglycemia has a profound effect on gastric motility. However, little is known about the site and mechanism that sense alteration in blood glucose level. The identification of glucose-sensing neurons in the nodose ganglia led us to hypothesize that hyperglycemia acts through vagal afferent pathways to inhibit gastric motility. With the use of a glucose-clamp rat model, we showed that glucose decreased intragastric pressure in a dose-dependent manner. In contrast to intravenous infusion of glucose, intracisternal injection of glucose at 250 and 500 mg/dl had little effect on intragastric pressure. Pretreatment with hexamethonium, as well as truncal vagotomy, abolished the gastric motor responses to hyperglycemia (250 mg/dl), and perivagal and gastroduodenal applications of capsaicin significantly reduced the gastric responses to hyperglycemia. In contrast, hyperglycemia had no effect on the gastric contraction induced by electrical field stimulation or carbachol ([10.sup.-5] M). To rule out involvement of serotonergic pathways, we showed that neither granisetron (5-[HT.sub.3] antagonist, 0.5 g/kg) nor pharmacological depletion of 5-HT using p-chlorophenylalanine (5-HT synthesis inhibitor) affected gastric relaxation induced by hyperglycemia. Lastly, [N.sup.G]-nitro-L-arginine methyl ester (LNAME) and a VIP antagonist each partially reduced gastric relaxation induced by hyperglycemia and, in combination, completely abolished gastric responses. In conclusion, hyperglycemia inhibits gastric motility through a capsaicin-sensitive vagal afferent pathway originating from the gastroduodenal mucosa. Hyperglycemia stimulates vagal afferents, which, in turn, activate vagal efferent cholinergic pathways synapsing with intragastric nitric oxide- and VIP-containing neurons to mediate gastric relaxation. nitric oxide; peptide VIP; glucose; nodose ganglia

Thyrotoxicosis is known to induce a broad range of changes in carbohydrate metabolism. Recent studies have identified the sympathetic and parasympathetic nervous system as major regulators of hepatic glucose metabolism. The present study aimed to investigate the pathogenesis of altered endogenous glucose production (EGP) in rats with mild thyrotoxicosis. Rats were treated with methimazole in drinking water and L-thyroxine ([T.sub.4]) from osmotic minipumps to either reinstate euthyroidism or induce thyrotoxicosis. Euthyroid and thyrotoxic rats underwent either a sham operation, a selective hepatic sympathetic denervation (Sx), or a parasympathetic denervation (Px). After 10 days of [T.sub.4] administration, all animals were submitted to a hyperinsulinemic euglycemic clamp combined with stable isotope dilution to measure EGP. Plasma triiodothyronine ([T.sub.3]) showed a fourfold increase in thyrotoxic compared with euthyroid animals. EGP was increased by 45% in thyrotoxic compared with euthyroid rats and correlated significantly with plasma [T.sub.3]. In thyrotoxic rats, hepatic PEPCK mRNA expression was increased 3.5-fold. Relative suppression of EGP during hyperinsulinemia was 34% less in thyrotoxic than in euthyroid rats, indicating hepatic insulin resistance. During thyrotoxicosis, Sx attenuated the increase in EGP, whereas Px resulted in increased plasma insulin with unaltered EGP compared with intact animals, compatible with a further decrease in hepatic insulin sensitivity. We conclude that chronic, mild thyrotoxicosis in rats increases EGP, whereas it decreases hepatic insulin sensitivity. Sympathetic hepatic innervation contributes only to a limited extent to increased EGP during thyrotoxicosis, whereas parasympathetic hepatic innervation may function to restrain EGP in this condition. thyroid hormone; autonomic nervous system; sympathetic; parasympathetic

Xanthine oxidase (XO)-derived reactive oxygen species (ROS) formation contributes to experimental chronic hypoxic pulmonary hypertension in adults, but its role in neonatal pulmonary hypertension has received little attention. In rats chronically exposed to hypoxia (13% [O.sub.2]) for 14 days from birth, we examined the effects of ROS scavengers (U74389G 10 mg*[kg.sup.-1]*[day.sup.-1] or Tempol 100 mg*[kg.sup.-1]*[day.sup.-1] ip) or a XO inhibitor, Allopurinol (50 mg*[kg .sup.-1]*[day.sup.-1] ip). Both ROS scavengers limited oxidative stress in the lung and attenuated hypoxia-induced vascular remodeling, confirming a critical role for ROS in this model. However, both interventions also significantly inhibited somatic growth and normal cellular proliferation in distal air spaces. Hypoxiaexposed pups had evidence of increased serum and lung XO activity, increased vascular XO-derived superoxide production, and vascular nitrotyrosine formation. These changes were all prevented by treatment with Allopurinol, which also attenuated hypoxia-induced vascular remodeling and partially reversed inhibited endothelium-dependent arterial relaxation, without affecting normal growth and proliferation. Collectively, our findings suggest that XO-derived superoxide induces endothelial dysfunction, thus impairing pulmonary arterial relaxation, and contributes to vascular remodeling in hypoxia-exposed neonatal rats. Due to the potential for adverse effects on normal growth, targeting XO may represent a superior 'antioxidant' strategy to ROS scavengers for neonates with pulmonary hypertension. antioxidants; allopurinol; U74389G; Tempol; 8-isoprostane

Insulin resistance (LR) is a hallmark of pregnancy. Because increased visceral fat (VF) is associated with IR in nonpregnant states, we reasoned that fat accretion might be important in the development of IR during pregnancy. To determine whether VF depots increase in pregnancy and whether VF contributes to IR, we studied three groups of 6-too-old female Sprague-Dawley rats: 1) nonpregnant sham-operated rats (Nonpreg; n = 6), 2) pregnant sham-operated rats (Preg; n = 6), and 3) pregnant rats in which VF was surgically removed 1 mo before mating (PVF-; n = 6). VF doubled by day 19 of pregnancy (Nonpreg 5.1 [+ or -] 0.3, Preg 10.0 [+ or -] 1.0 g, P < 0.01), and PVF- had similar amounts of VF compared with Nonpreg (PVF- 4.6 [+ or -] 0.8 g). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp in late gestation in chronically catheterized unstressed rats. Glucose IR (mg*[kg.sup.-1]*[min.sup.-1]) was highest in Nonpreg (19.4 [+ or -] 2.0), lowest in Preg (11.1 [+ or -] 1.4), and intermediate in PVF- (14.7 [+ or -] 0.6; P < 0.001 between all groups). During the clamp, Nonpreg had greater hepatic insulin sensitivity than Preg [hepatic glucose production (HGP): Nonpreg 4.5 [+ or -] 1.3, Preg 9.3 [+ or -] 0.5 mg*[kg.sup.-1]*[min.sup.-1]; P < 0.001]. With decreased VF, hepatic insulin sensitivity was similar to nonpregnant levels in PVF- (HGP 4.9 [+ or -] 0.8 mg*[kg.sup.-1]*[min.sup.-1]). Both pregnant groups had lower peripheral glucose uptake compared with Nonpreg. In parallel with hepatic insulin sensitivity, hepatic triglyceride content was increased in pregnancy (Nonpreg 1.9 [+ or -] 0.4 vs. Preg 3.2 [+ or -]- 0.3 mg/g) and decreased with removal of VF (PVF- 1.3 [+ or -] 0.4 mg/g; P < 0.05). Accretion of visceral fat is an important component in the development of hepatic IR in pregnancy, and accumulation of hepatic triglycerides is a mechanism by which visceral fat may modulate insulin action in pregnancy. triglyceride; free fatty acids; adipokines

Diabetes affects many aspects of gastrointestinal motility, in part due to changes in interstitial cells of Cajal (ICC). The effect of diabetes on the colon, however, is not well characterized, and the aim of the present study was to investigate possible relationships between altered colonic motility as a consequence of streptozotocin-induced diabetes and injury to ICC. Physiological, immunohistochemical, and ultrastructural techniques were employed. The motor pattern of the rat colon was dominated by rhythmic high-amplitude, low-frequency contractions that were primarily myogenic in origin. These rhythmic contractions were induced by stretch associated with increased tension; the amplitude of the superimposed rhythmic contractions increased with increasing applied tension. In diabetic rats, the stretch-induced rhythmic contractile activity remained robust and of similar frequency but was significantly higher in amplitude compared with that in control rats. At 700 mg of applied tension, the force of contraction in circular colonic muscle strips of the diabetic rats was 370% of control values. This robust presence of low-frequency contractions is consistent with the unaffected pacemaker, the ICC associated with Auerbach's plexus, and the increased amplitude correlates with loss of and injury to ICC of the submuscular plexus and intramuscular ICC. Loss of inhibitory nitrergic nerves does not appear to be a factor based on unaltered nNOS immunoreactivity. diabetes; interstitial cells of Cajal; immunohistochemical staining; rhythmic contractile activity; motility

Rats with experimental colitis suffer from impaired gastric emptying (GE). We previously showed that this phenomenon involves afferent neurons within the pelvic nerve. In this study, we aimed to identify the mediators involved in this afferent hyperactivation. Colitis was induced by trinitrobenzene sulfate (TNBS) instillation. We determined GE, distal front, and geometric center (GC) of intestinal transit 30 min after intragastric administration of a semiliquid Evans blue solution. We evaluated the effects of the transient receptor potential vanilloid type 1 (TRPV1) antagonists capsazepine (5-10 mg/kg) and N-(4-tertiarybutylphenyl)-4-(3-cholorphyridin-2-yl) tetrahydropyrazine-1(2H)carboxamide (BCTC; 1-10 mg/kg) and the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37) (150 [micro]g/ kg). To determine TRPV1 receptor antagonist sensitivity, we examined their effect on capsaicin-induced relaxations of isolated gastric fundus muscle strips. Immunocytochemical staining of TRPV1 and RT-PCR analysis of TRPV1 mRNA were performed in dorsal root ganglion (DRG) L6-S1. TNBS-induced colitis reduced GE but had no effect on intestinal motility. Capsazepine reduced GE in controls but had no effect in rats with colitis. At doses that had no effects in controls, BCTC and CGRP-(8-37) significantly improved colitis-induced gastroparesis. Capsazepine inhibited capsaicin-induced relaxations by 35% whereas BCTC completely abolished them. TNBS-induced colitis increased TRPV1-like immunoreactivity and TRPV1 mRNA content in pelvic afferent neuronal cell bodies in DRG L6-S1. In conclusion, distal colitis in rats impairs GE via sensitized pelvic afferent neurons. We provided pharmacological, immunocytochemical, and molecular biological evidence that this sensitization is mediated by TRPV1 receptors and involves CGRP release. gastric emptying; sensory nerve; pelvic nerve; CGRP

The adult Goto-Kakizaki (GK) rat is characterized by impaired glucose-induced insulin secretion in vivo and in vitro, decreased [beta]-cell mass, decreased insulin sensitivity in the liver, and moderate insulin resistance in muscles and adipose tissue. GK rats do not exhibit basal hyperglycemia during the first 3 wk after birth and therefore could be considered prediabetic during this period. Our aim was to identify the initial pathophysiological changes occurring during the prediabetes period in this model of type 2 diabetes (T2DM). To address this, we investigated [beta]-cell function, insulin sensitivity, and body composition in normoglycemic prediabetic GK rats. Our results revealed that the in vivo secretory response of GK [beta]-cells to glucose is markedly reduced and the whole body insulin sensitivity is increased in the prediabetic GK rats in vivo. Moreover, the body composition of suckling GK rats is altered compared with age-matched Wistar rats, with an increase of the number of adipocytes before weaning despite a decreased body weight and lean mass in the GK rats. None of these changes appeared to be due to the postnatal nutritional environment of GK pups as demonstrated by cross-fostering GK pups with nondiabetic Wistar dams. In conclusion, in the GK model of T2DM, [beta]-cell dysfunction associated with increased insulin sensitivity and the alteration of body composition are proximal events that might contribute to the establishment of overt diabetes in adult GK rats. Goto-Kakizaki rat; body composition; insulin sensitivity; glucose tolerance

Although alcohol abuse is the major cause of chronic pancreatitis, the pathogenesis of alcoholic chronic pancreatitis (ACP) remains obscure. A critical obstacle to understanding the mechanism of ACP is lack of animal models. Our objective was to develop one such model. Rats were pair-fed for 8 wk ethanol or control Lieber-DeCarli liquid diet. For the last 2 wk, they received cyclosporin A (CsA; 20 mg/kg once daily) or vehicle. After 1 wk on CsA, one episode of acute pancreatitis was induced by four 20 [micro]g/kg injections of cerulein (Cer); controls received saline. Pancreas was analyzed 1 wk after the acute pancreatitis. CsA or Cer treatments alone did not result in pancreatic injury in either control (C)- or ethanol (E)-fed rats. We found, however, that alcohol dramatically aggravated pathological effect of the combined CsA+Cer treatment on pancreas, resulting in massive loss of acinar cells, persistent inflammatory infiltration, and fibrosis. Macrophages were prominent in the inflammatory infiltrate. Compared with control-fed C+CsA+Cer rats, their ethanol-fed E+CsA+Cer counterparts showed marked increases in pancreatic NF-[kappa]B activation and cytokine/chemokine mRNA expression, collagen and fihronectin, the expression and activities of matrix metalloproteinase-2 and -9, and activation of pancreatic stellate cells. Thus we have developed a model of alcohol-mediated postacute pancreatitis that reproduces three key responses of human ACP: loss of parenchyma, sustained inflammation, and fibrosis. The results indicate that alcohol impairs recovery from acute pancreatitis, suggesting a mechanism by which alcohol sensitizes pancreas to chronic injury. ethanol; inflammatory response; pancreatic stellate cells; cerulein; cyclosporin A

The mitochondrial pyruvate dehydrogenase complex (PDC) is inactivated in many tissues during starvation and diabetes. We investigated carbohydrate oxidation (CHO) and the regulation of the PDC in lean and obese Zucker diabetic fatty (ZDF) rats during fed and starved conditions as well as during an oral glucose load without and with pharmacologically reduced levels of free fatty acids (FFA) to estimate the relative contribution of FFA on glucose tolerance, CHO, and PDC activity. The increase in total PDC activity (20-45%) was paralleled by increased protein levels (~2-fold) of PDC subunits in liver and muscle of obese ZDF rats. Pyruvate dehydrogenase kinase-4 (PDK4) protein levels were higher in obese rats, and consequently PDC activity was reduced. Although PDK4 protein levels were rapidly downregulated (57-62%) in both lean and obese animals within 2 h after glucose challenge, CHO over 3 h as well as the peak of PDC activity (1 h after glucose load) in liver and muscle were significantly lower in obese rats compared with lean rats. Similar differences were obtained with pharmacologically suppressed FFA by nicotinic acid, but with significantly improved glucose tolerance in obese rats, as well as increased CHO and delta increases in PDC activity (0-60 min) both in muscle and liver. These results demonstrated the suppressive role of FFA acids on the measured parameters. Furthermore, the results clearly demonstrate a rapid reactivation of PDC in liver and muscle of lean and obese rats after a glucose load and show that PDC activity is significantly lower in obese ZDF rats. glucose oxidation; glucose tolerance test; insulin resistance; diabetes; pyruvate dehydrogenase kinase-4

The common hepatic branch of the vagus nerve negatively regulates lard intake in rats with streptozotocin (STZ)-induced, insulin-dependent diabetes. However, this branch consists of two subbranches: the hepatic branch proper, which serves the liver, and the gastroduodenal branch, which serves the distal stomach, pancreas, and duodenum. The aim of this study was to determine whether the gastroduodenal branch specifically regulates voluntary lard intake. We performed a gastroduodenal branch vagotomy (GV) on nondiabetic, STZ-diabetic, and STZ-diabetic insulin-treated groups of rats and compared them with sham-operated counterparts. All rats had high steady-state corticosterone levels to maximize lard intake. Five days after surgery, all rats were provided with the choice of chow or lard to eat for another 5 days. STZ-diabetes resulted in a reduction in lard intake that was partially rescued by either GV or insulin treatment. Patterns of white adipose tissue (WAT) deposition differed after GV- and insulin-induced lard intake, with subcutaneous WAT increasing exclusively after the former and mesenteric WAT increasing exclusively in the latter. GV also prevented the insulin-induced reduction in the STZ-elevated plasma glucagon, triglycerides, free fatty acids, and total ketone bodies but did not alter the effect of insulin-induced reduction of plasma glucose levels. These data suggest that the gastroduodenal branch of the vagus inhibits lard intake and regulates WAT deposition and plasma metabolite levels in STZ-diabetic rats. insulin; glucocorticoids; obesity; diabetes; food intake

Sphingosine 1-phosphate (S1P) mediates a number of cellular responses, including growth and proliferation. Skeletal muscle possesses the full enzymatic machinery to generate SIP and expresses the transcripts of S 1P receptors. The aim of this work was to localize SIP receptors in rat skeletal muscle and to investigate whether SIP exerts atrophic action on muscle fibers. RT-PCR and Western blot analyses demonstrated the expression of [S1P.sub.1] and [S1P.sub.3] receptors by soleus muscle. Immunofluorescence revealed that [S1P.sub.1] and [S1P.sub.3] receptors are localized at the cell membrane of muscle fibers and in the T-tubule membranes. The receptors also decorate the nuclear membrane. [S1P.sub.1] receptors were also present at the neuromuscular junction. The possible trophic action of S1P was investigated by utilizing the denervation atrophy model. Rat soleus muscle was analyzed 7 and 14 days after motor nerve cut. During denervation, S1P was continuously delivered to the muscle through a mini osmotic pump. S1P and its precursor, sphingosine (Sph), significantly attenuated the progress of denervation-induced muscle atrophy. The trophic effect of Sph was prevented by N,N-dimethylsphingosine, an inhibitor of Sph kinase, the enzyme that converts Sph into S1P. Neutralization of circulating S1P by a specific antibody further demonstrated that S1P was responsible for the trophic effects of S1P during denervation atrophy. Denervation produced the down regulation of [S1P.sub.1] and [S1P.sub.3] receptors, regardless of the presence of the receptor agonist. In conclusion, the results suggest that S1P acts as atrophic factor of skeletal muscle. sphingosine 1-phosphate receptors; sphingomyelin derivatives; skeletal muscle atrophy

A study was made of the 'rundown' of [GABA.sub.A] receptors, micro-transplanted to Xenopus oocytes from surgically resected brain tissues of patients afflicted with drug-resistant human mesial temporal lobe epilepsy (mTLE). Cell membranes, isolated from mTLE neocortex specimens, were injected into frog oocytes that rapidly incorporated functional [GABA.sub.A] receptors. Upon repetitive activation with GABA (1 mM), 'epileptic' [GABA.sub.A] receptors exhibited a [GABA.sub.A]-current ([I.sub.GABA]) rundown that was significantly enhanced by [Zn.sup.2+] ([less than or equal to]250 [micro]M), and practically abolished by the high-affinity [GABA.sub.A] receptor inverse agonist SR95531 (gabazine; 2.5-25 [micro]M). Conversely, [IGAB.sub.A] generated by 'control' [GABA.sub.A] receptors microtransplanted from nonepileptic temporal lobe, lesional TLE, or authoptic disease-free tissues remained stable during repetitive stimulation, even in oocytes treated with [Zn.sup.2+]. We conclude that rundown of mTLE epileptic receptors depends on the presence of 'phasic [GABA.sub.A] receptors' that have low sensitivity to antagonism by [Zn.sup.2+]. Additionally, we found that [GABA.sub.A] receptors, microtransplanted from the cerebral cortex of adult rats exhibiting recurrent seizures, caused by pilocarpine-induced status epilepticus, showed greater rundown than control tissue, an event also occurring in patch-clamped rat pyramidal neurons. Rundown of epileptic rat receptors resembled that of human mTLE receptors, being enhanced by [Zn.sup.2+] (40 [micro]M) and sensitive to the antiepileptic agent levetiracetam, the neurotrophin brain-derived neurotrophic factor, and the phosphatase blocker okadaic acid. Our findings point to the rundown of [GABA.sub.A] receptors as a hallmark of TLE and suggest that modulating tonic and phasic mTLE [GABA.sub.A] receptor activity may represent a useful therapeutic approach to the disease. Xenopus oocytes | tonic | epileptic rat

The pudendal nerve innervates the external urethral sphincter (EUS) and is among the tissues injured during childbirth, which may lead to symptoms of stress urinary incontinence (SUI). To understand the mechanisms of injury and repair, urethral leak-point pressure (LPP) was measured 4 days, 2 wk, or 6 wk after bilateral pudendal nerve crush. Morphometric changes in the distal nerve and EUS were examined by light and electron microscopy. To determine whether recovery resulted from pudendal neuroregeneration, LPP was measured before and after pudendal nerve transection 2 wk after nerve crush. LPP was significantly decreased 4 days after pudendal nerve crush compared with sham-injured animals as well as 2 or 6 wk after nerve crush. LPP was not significantly different 2 or 6 wk after nerve crush compared with sham-injured animals, suggesting that urethral function had returned to normal. Four days after pudendal nerve crush, the EUS branch of the pudendal nerve distal to the injury site showed evidence of nerve degeneration and the EUS appeared disrupted. Two weeks after nerve crush, the distal nerve and EUS both showed evidence of both nerve degeneration and recovery. Two weeks after nerve crush, LPP was significantly decreased after nerve transection. Six weeks after nerve injury, evidence of neuroregeneration was observed in the pudendal nerve and the EUS. This study has demonstrated that functional recovery and neuroregeneration are significant 2 wk after nerve crush, although by anatomical assessment, recovery appears incomplete, suggesting that 2 wk represents an early time point of initial neuroregeneration. leak point pressure; urinary incontinence; voiding; pudendal nerve; urethra; Sprague-Dawley

We searched for synchronization among autoregulation mechanisms using wavelet transforms applied to tubular pressure recordings in nephron pairs from the surface of rat kidneys. Nephrons have two oscillatory modes in the regulation of their pressures and flows: a faster (100-200 mHz) myogenic mode, and a slower (20-40 mHz) oscillation in tubuloglomerular feedback (TGF). These mechanisms interact; the TGF mode modulates both the amplitude and the frequency of the myogenic mode. Nephrons also communicate with each other using vascular signals triggered by membrane events in arteriolar smooth muscle cells. In addition, the TGF oscillation changes in hypertension to an irregular fluctuation with characteristics of deterministic chaos. The analysis shows that, within single nephrons of normotensive rats, the myogenic mode and TGF are synchronized at discrete frequency ratios, with 5:1 most common. There is no distinct synchronization ratio in spontaneously hypertensive rats (SHR). In normotensive rats, full synchronization of both TGF and myogenic modes is the most probable state for pairs of nephrons originating in a common cortical radial artery. For SHR, full synchronization is less probable; most common in SHR is a state of partial synchronization with entrainment between neighboring nephrons for only one of the modes. Modulation of the myogenic mode by the TGF mode is much stronger in hypertensive than in normotensive rats. Synchronization among nephrons forms the basis for an integrated reaction to blood pressure fluctuations. Reduced synchronization in SHR suggests that the effectiveness of the coordinated response is impaired in hypertension. tubuloglomerular feedback; myogenic mechanism; oscillations; wavelet analysis

Microalbuminuria is an early sign of diabetic nephropathy. The aim of the present study was to investigate whether the changes of the glomerular filtration barrier in early experimental diabetes are due to size- or charge-selective alterations. Wistar rats, made diabetic by streptozotocin (STZ) and having their blood glucose maintained at ~20 mM for 3 or 9 wk, were compared with age-matched controls. Glomerular clearances of native albumin (C1-HSA) and neutralized albumin (CI-nHSA) were assessed using a renal uptake technique. Glomerular filtration rate and renal plasma flow were assessed using [sup.51]Cr-EDTA and [[125.sup]I]iodohippurate, respectively. In a separate set of animals, diabetic for 9 wk, and in controls, glomerular sieving coefficients (0) for neutral FITC-Ficoll (molecular radius: 15-90 [Angstrom]) were assessed using size exclusion chromatography. At 3 wk of diabetes, CI-HSA and CI-nHSA remained unchanged, indicating no alteration in either size or charge selectivity. By contrast, at 9 wk of diabetes, there was a twofold increase of C1-HSA, whereas CI-nHSA remained largely unchanged, at first suggesting a glomerular charge defect. However, according to a two-pore model, the number of large pores, assessed from both Ficoll and C1-HSA, increased twofold. In addition, a small reduction in proximal tubular reabsorption was observed at 3 wk, which was further reduced at 9 wk. In conclusion, no functional changes were observed in the glomerular filtration barrier at 3 wk of STZ-induced diabetes, whereas at 9 wk there was a decrease in size selectivity due to an increased number of large glomerular pores. sieving coefficient; proteinuria; capillary permeability; fractional clearance; macromolecules; diabetic nephropathy

Visceral organ 'cross talk' is suspected to contribute to multiorgan symptomatology found in conditions such as irritable bowel syndrome and interstitial cystitis. The goal of the present study was to investigate the short- and long-term effects of acute colitis on bladder detrusor muscle contractility. We hypothesized that inflammation of the colon leads to changes in bladder function via direct changes in detrusor smooth muscle contractility. In this study, colonic inflammation was induced in male rats via an enema of trinitrobenzenesulfonic acid (TNBS) (50 mg/kg, 0.5 ml, 25% ethanol). Colitis was confirmed using gross morphology, histology, and measurements of myeloperoxidase activity. Saline enema-treated rats served as controls. Three, 15, and 30 days post-enema treatment, bladder detrusor muscle contractility was investigated in response to electrical field stimulation (EFS), cholinergic agonism with carbachol (CCh), and KCl. During active colonic inflammation (day 3 post-TNBS enema), the bladder detrusor muscle appeared normal and showed no significant inflammation. However, abnormalities in bladder detrusor muscle contractility occurred in response to EFS and CCh but not KCl. During and after recovery from colonic inflammation (days 15 and 30 post-TNBS enema), changes in bladder detrusor muscle contractility in response to EFS and CCh returned to control levels. We found that a transient colonic inflammatory insult significantly attenuates the amplitude of bladder detrusor muscle contractions in vitro, at least in part, through changes in cholinergic innervation, which are reversible after recovery from the colitis. trinitrobenzenesulfonic acid; colon; detrusor muscle; rat

Calcineurin, a [Ca.sup.2+] -regulated protein phosphatase, links myocardial [Ca.sup.2+] signaling with hypertrophic gene transcription. Calcineurin abundance increases in pressure-overload hypertrophy and may reduce agonist-mediated phospholamban (PLB) phosphorylation to underlie blunted [beta]-adrenergic receptor ([beta]-AR) responsiveness in hypertension. This hypothesis was tested by measuring the effects of calcineurin inhibition on changes in cardiac contractility caused by [beta]-adrenergic stimulation in spontaneously hypertensive rats (SHR). Female SHR (age: 7 mo) and age-matched female Wistar-Kyoto rats (WKY) were studied. Heart weight-to-body weight ratio (P < 0.01) and systolic blood pressure (P < 0.01) were greater in SHR compared with WKY and were associated with increased myocardial calcineurin mRNA (CnA[beta]) and activity (P < 0.05). [beta]-AR stimulation with isoproterenol (Iso) increased calcineurin activity (P < 0.05) in both WKY and SHR hearts, and this activity was suppressed with cyclosporin A (CsA) treatment. In SHR, CsA improved left ventricular whole heart and isolated myocyte [beta]-AR responsiveness by normalizing PLB phosphorylation at [Ser.sup.16] and [Thr.sup.17] (P < 0.05). These CsA-induced, PLB-mediated effects were associated with an augmentation in cardiomyocyte peak [Ca.sup.2+] and a reduced rate (time constant of isovolumic pressure relaxation, tau) and magnitude of diastolic [Ca.sup.2+] during [beta]-AR stimulation. In conclusion, CsA normalized the blunted [beta]-AR responsiveness associated with hypertension, in part, by mitigating calcineurin activity while improving PLB phosphorylation and subsequent sarcoplasmic reticulum [Ca.sup.2+] regulation. myocardium; hypertrophy; phosphatase; protein kinase A; calcium calmodulin kinase II

Aging impairs shear-stress-dependent dilation of arteries via increased superoxide production, decreased SOD activity, and decreased activation of endothelial nitric oxide (NO) synthase (eNOS). In the present study, we investigated whether chronic increases in shear stress, elicited by increases in blood flow, would improve vascular endothelial function of aged rats. To this end, second-order mesenteric arteries of young (6 too) and aged (24 too) male Fischer-344 rats were selectively ligated for 3 wk to elevate blood flow in a first-order artery [high blood flow (HF)]. An in vitro study was then conducted on first-order arteries with HF and normal blood flow (NF) to assess shear stress (1, 10, and 20 dyn/[cm.sup.2])-induced release of NO into the perfusate. In HF arteries of both age groups, shear stress-induced NO production increased significantly. In 24-too-old rats, the reduced shear stress-induced NO production in NF arteries was normalized by HF to a level similar to that in NF arteries of 6-too-old rats. The increased NO production in HF arteries of 24-mo-old rats was associated with increased shear stress-induced dilation, expression of eNOS protein, and shear stress-induced eNOS phosphorylation. Wortmannin, a phosphatidylinositol 3-kinase inhibitor, reduced shear stress-induced eNOS phosphorylation and vasodilation. Superoxide production decreased significantly in HF compared with NF arteries in 24-too-old rats. The decreased superoxide production was associated with significant increases in CuZn-SOD and extracellular SOD protein expressions and total SOD activity. These results suggest that stimulation with chronic HF restores shear-stress-induced activation of eNOS and antioxidant ability in aged arteries. endothelium; endothelial nitric oxide synthase phosphorylation; arterial ligation

We reported previously that intermittent hypoxia with C[O.sub.2] to maintain eucapnia (IH-C) elevates plasma endothelin-1 (ET-1) and arterial pressure. In small mesenteric arteries (sMA; inner diameter = 150 [micro]m), IH-C augments ET-1 constrictor sensitivity but diminishes ET-l-induced increases in intracellular [Ca.sup.2+] concentration, suggesting IH-C exposure increases both ET-1 levels and ET-l-stimulated [Ca.sup.2+] sensitization. Because Rho-associated kinase (ROK) can mediate [Ca.sup.2+] sensitization, we hypothesized that augmented vasoconstrictor sensitivity to ET-1 in arteries from IH-C-exposed rats is dependent on ROK activation. In thoracic aortic rings, ET-1 contraction was not different between groups, but ROK inhibition (Y-27632, 3 and 10 [micro]M) attenuated ET-1 contraction more in IH-C than in sham arteries (50 [+ or -] 11 and 78 [+ or -] 7% vs. 41 [+ or -] 12 and 48 [+ or -] 9% inhibition, respectively). Therefore, ROK appears to contribute more to ET-1 contraction in IH-C than in sham aorta. In sMA, ROK inhibitors did not affect ET-1-mediated constriction in sham arteries and only modestly inhibited it in IH-C arteries. In ionomycin-permeabilized sMA with intracellular [Ca.sup.2+] concentration held at basal levels, Y-27632 did not affect ET-l-mediated constriction in either IH-C or sham sMA and ET-1 did not stimulate ROK translocation. In contrast, inhibition of myosin light-chain kinase (ML-9, 100 [micro]M) prevented ET-1-mediated constriction in sMA from both groups. Therefore, IH-C exposure increases ET-1 vasoconstrictor sensitivity in sMA but not in aorta. Furthermore, ET-1 constriction is myosin light-chain kinase dependent and mediated by [Ca.sup.2+] sensitization that is independent of ROK activation in sMA but not aorta. Thus ET-1-mediated signaling in aorta and sMA is altered by IH-C but is dependent on different second messenger systems in small vs. large arteries. sleep apnea; endothelin-1; vascular smooth muscle cells; Rho-associated kinase

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions, particularly in septic shock. The intracellular mechanisms involved in the effect of ADM on adult rat ventricular myocytes are still to be elucidated. Ventricular myocytes were isolated from adult rats 4 h after an intraperitoneal injection of lipopolysaccharide (LPS, 10 mg/kg). Membrane potential and L-type calcium current ([I.sub.Ca, L]) were determined using whole cell patch-clamp methods. APD in LPS group was significantly shorter than control values (time to 50% repolarization: LPS, 169 [+ or -] 2 ms; control, 257 [+ or -] 2 ms, P < 0.05; time to 90% repolarization: LPS, 220 [+ or -] 2 ms; control, 305 [+ or -] 2 ms, P < 0.05). [I.sub.ca,L] density was significantly reduced in myocytes from the LPS group (-3.2 [+ or -] 0.8 pA/pF) compared with that of control myocytes (-6.7 [+ or -] 0.3 pA/pF, P < 0.05). The ADM antagonist ADM-(22-52) reversed the shortened APD and abolished the reduction of [I.sub.Ca.L] in shock myocytes. In myocytes from control rats, incubating with ADM for 1 h induced a marked decrease in peak [I.sub.Ca,L] density. This effect was reversed by ADM-(22-52). The [G.sub.i] protein inhibitor, pertussis toxin (PTX), the protein kinase A (PKA) inhibitor, KT-5720, and the specific cyclo-oxygenase 2 (COX-2) inhibitor, nimesulide, reversed the LPS-induced reduction in peak [I.sub.Ca.L]. The results suggest a COX-2-involved PKA-dependent switch from [G.sub.s] coupled to PTX-sensitive [G.sub.i] coupling by ADM in adult rat ventricular myocytes. The present study delineates the intracellular pathways involved in ADM-mediated effects on [I.sub.Ca.L] in adult rat ventricular myocytes and also suggests a role of ADM in sepsis. pertussis toxin; protein kinase A inhibitor

Angiotensin (ANG) II activating type 1 receptors (ATIRs) enhances superoxide anion ([O.sub.2.sup.*-]) and arachidonate (AA) formation. AA is metabolized by cyclooxygenases (COXs) to [PGH.sub.2], which is metabolized by thromboxane (Tx)[A.sub.2] synthase to Tx[A.sub.2] or oxidized to 8-isoprostane [PGF.sub.2[alpha]] (8-Iso) by [O.sub.*-]. [PGH.sub.2], Tx[A.sub.2], and 8-Iso activate thromboxane-prostanoid receptors (TPRs). We investigated whether blood pressure in a rat model of early (3 wk) two-kidney, one-clip (2K,1C) Goldblatt hypertension is maintained by [AT.sub.1]Rs or [AT.sub.2]Rs, driving COX-1 or -2-dependent products that activate TPRs. Compared with sham-operated rats, 2K,1C Goldblatt rats had increased mean arterial pressure (MAP; 120 [+ or -] 4 vs. 155 [+ or -] 3 mmHg; P < 0.001), plasma renin activity (PRA; 22 [+ or -] 7 vs. 48 [+ or -] 5 ng x [m1.sup.-1] x [h.sup.-l]; P < 0.01), plasma malondialdehyde (1.07 [+ or -] 0.05 vs. 1.58 [+ or -] 0.16 nmol/1; P < 0.01), and Tx[B.sub.2] excretion (26 [+ or -] 4 vs. 51 [+ or -] 7 ng/24 h; P < 0.01). Acute graded intravenous doses of benazeprilat (angiotensin-converting enzyme inhibitor) reduced MAP at 20 min (-36 [+ or -] 5 mmHg; P < 0.001) and excretion of Tx[A.sub.2] metabolites. Indomethacin (nonselective COX antagonist) or SC-560 (COX-1 antagonist) reduced MAP at 20 min (-25 [+ or -] 5 and -28 [+ or -] 7 mmHg; P < 0.001), whereas valdecoxib (COX-2 antagonist) was ineffective (-9 [+ or -] 5 mmHg; not significant). Losartan ([ATI.sub.1]R antagonist) or SQ-29548 (TPR antagonist) reduced MAP at 150 min (-24 [+ or -] 6 and -22 [+ or -] 3 mmHg; P < 0.001), whereas PD-123319 ([AT.sub.2]R antagonist) was ineffective. Acute blockade of TPRs, COX-1, or COX-2 did not change PRA, but Tx[B.sub.2] generation by the clipped kidney was reduced by blockade of COX-1 and increased by blockade of COX-2.2K, 1C hypertension in rats activates renin, [O.sub.2.sup*-], and vasoconstrictor PGs. Hypertension is maintained by [AT.sub.1]Rs and by COX-1, but not COX-2, products that activate TPRs. renovascular hypertension; angiotensin receptor blocker; thromboxane [A.sub.2]; isoprostane; angiotensin-converting enzyme inhibition

Recent studies have established that age is the major risk factor for vascular disease. Numerous aberrant changes occur in vascular structure and function during aging, and animal models are the primary means to determine the underlying mechanisms of age-mediated vascular pathology. The Fischer 344/Brown Norway F1 hybrid (F344xBN) rat thoracic aorta has been shown to display age-related pathology similar to what occurs in humans. This study utilized the F344xBN rat aorta and both morphometric and global gene expression analyses to identify appropriate time points to study vascular aging and to identify molecules associated with the development and progression of vascular pathology. In contrast to some previous studies that indicated age-related abrupt changes, a progressive increase in intimal and medial thickness, as well as smooth muscle cell-containing intimal protrusions, was observed in thoracic aorta. This structural vascular pathology was associated with a progressive, but nonlinear, increase in global differential gene expression. Gene products with altered mRNA and protein expression included inflammation-related molecules: specifically, the adhesion molecules ICAM-1 and VCAM-1 and the bone morphogenic proteins osteopontin and bone sialoprotein-1. Intimal-associated macrophages were found to increase significantly in number with age. Both systemic and tissue markers of oxidant stress, serum 8-isoprostane and 3-nitrotyrosine, respectively, were also found to increase during aging. The results demonstrate that major structural abnormalities and altered gene expression develop after 6 mo and that the progressive pathological development is associated with increased inflammation and oxidant stress. arterial remodeling; inflammation; microarray; oxidative stress

Vascular endothelial growth factor (VEGF) receptor blockade impairs lung growth and decreases nitric oxide (NO) production in neonatal rat lungs. Inhaled NO (iNO) treatment after VEGF inhibition preserves lung growth in infant rats by unknown mechanisms. We hypothesized that neonatal VEGF inhibition disrupts lung growth by causing apoptosis in endothelial cells, which is attenuated by early iNO treatment. Three-day-old rats received SU-5416, an inhibitor of VEGF receptor, or its vehicle and were raised in room air with or without iNO (10 ppm). SU-5416 reduced alveolar counts and lung vessel density by 28% (P < 0.005) and 21% (P < 0.05), respectively, as early as at 7 days of age. SU-5416 increased lung active caspase-3 protein by 60% at 5 days of age (P < 0.05), which subsided by 7 days of age, suggesting a transient increase in lung apoptosis after VEGF blockade. Apoptosis primarily colocalized to lung vascular endothelial cells, and SU-5416 increased endothelial cell apoptotic index by eightfold at 5 days of age (P vascular growth; alveolar growth; developing lung; bronchopulmonary dysplasia

Chronic obstructive pulmonary disease (COPD) is a smoking-related disease that lacks effective therapies due partly to the poor understanding of disease pathogenesis. The aim of this study was to identify molecular pathways that could be responsible for the damaging consequences of smoking. To do this, we employed Gene Set Enrichment Analysis to analyze differences in global gene expression, which we then related to the pathological changes induced by cigarette smoke (CS). Sprague-Dawley rats were exposed to whole body CS for 1 day and for various periods up to 8 too. Gene Set Enrichment Analysis of microarray data identified that metabolic processes were most significantly increased early in the response to CS. Gene sets involved in stress response and inflammation were also upregulated. CS exposure increased neutrophil chemokines, cytokines, and proteases (MMP-12) linked to the pathogenesis of COPD. After a transient acute response, the CS-exposed rats developed a distinct molecular signature after 2 wk, which was followed by the chronic phase of the response. During this phase, gene sets related to immunity and defense progressively increased and predominated at the later time points in smoke-exposed rats. Chronic CS inhalation recapitulated many of the phenotypic changes observed in COPD patients including oxidative damage to macrophages, a slowly resolving inflammation, epithelial damage, mucus hypersecretion, airway fibrosis, and emphysema. As such, it appears that metabolic pathways are central to dealing with the stress of CS exposure; however, over time, inflammation and stress response gene sets become the most significantly affected in the chronic response to CS. chronic obstructive pulmonary disease; metabolic pathways; oxidant stress

Temporal changes in physiological spaces, protein expression of transporters and enzymes, and enalapril removal were appraised in the metastatic liver tumor model developed from male Wag/Rij rats after the intraportal injection of CC531 colon adenocarcinoma cells; sham-operated preparations received PBS. Liver tissue spaces, investigated with multiple indicator dilution technique in liver perfusion studies, were unchanged at week 3 after tumor induction. At week 4, however, the sinusoidal blood volume and albumin Disse space in tumor-bearing livers were slightly lower compared with those of shams. Increased levels of the canalicular ATP transporters, P-glycoprotein, multidrug resistance-associated protein 2 (Mrp2), and bile salt export pump (Bsep) at week 2 (P < 0.05), unchanged levels of Ntcp, Oatplal, Oatpla4, and Mct2, but decreased levels of cytochrome P450 3a2 (Cyp3a2) and glutathione S-transferase (Gst4-4) at week 4 (P < 0.05) were observed in peritumor vs. shamoperated liver tissues with Western blotting. The steady-state extraction ratio of enalapril, a substrate that enters the liver rapidly via Oatplal and primarily undergoes metabolism by the carboxylesterases, was unaffected by liver metastasis at week 4 regardless of its delivery via the portal vein or hepatic artery into the perfused liver preparations. microcirculation; kinetics

Selective cyclooxygenase-2 (COX-2) inhibitors appear to have beneficial renoprotective effects in most, but not all, renal disease conditions. The objective of our study was to examine the effects of COX-2 inhibition in a rat model of polycystic kidney disease. Four-week-old Han:SPRD-cy rats were given a standard rodent diet containing NS-398 (3 mg.kg body [wt.sup-1].[day.sup.-1]) or a control diet without NS-398 for 7 wk. In diseased rats, selective COX-2 inhibition resulted in 18% and 67% reduction in cystic expansion and interstitial fibrosis, respectively, but no change in renal function. NS-398 also ameliorated disease-associated pathologies, such as renal inflammation, cell proliferation, and oxidant injury (by 33, 38, and 59%, respectively). Kidney disease was associated with elevated renal COX-1 and COX-2 enzyme activities, and NS-398 blunted the increase in COX-2 enzyme activity (as indicated by 21 and 28% lower renal thromboxane B2 and [PGE.sub.2] levels, respectively). NS-398 reduced urinary excretion of prostanoid metabolites in diseased rats. In summary, COX-2 inhibition attenuated renal injury, reduced the elevated renal COX-2 activity, and ameliorated disease-related alterations in prostanoid production in this rat model of chronic renal disease. NS-398; histology; cyclooxygenase activity

Syrian Golden hamsters develop severe emphysema after a single intratracheal dose of elastase, whereas Sprague-Dawley rats exhibit mild emphysema with the same dose per kilogram body weight. We hypothesized that the development of severe emphysema is prevented in rats by the high serum level of [alpha]1-antitrypsin reported in rats, compared with hamsters, which provides for a high lung elastase inhibitory capacity (EIC). To explore this possibility, we challenged the antiprotease system of the rats by treating them with three similar weekly doses of elastase. Four months after treatment, we evaluated changes in histology, volume, and elastic properties of rat lungs and compared them with those of hamsters receiving a single dose of elastase. We also measured serum [alpha]1-antitrypsin levels and serum and lung EIC in control rats and hamsters. Results showed that, in association with 40% less serum and lung EIC compared with rats (P < 0.001), hamster lungs had upperlobe bullae formation, severe microscopic emphysema, a fourfold increase in lung volume (P < 0.01) and a threefold increase in constant k, an index of compliance, of the lung deflation pressurevolume curve (P < 0.01). In contrast, rats developed mild emphysema, with only 50% increase in volume (P < 0.05) and 60% increase in constant k (P < 0.01). In conclusion, two species that differ in serum and lung EIC exhibit significant differences in emphysema development after elastase. Rats with high EIC, despite receiving three doses of elastase, showed significantly less derangement of morphological and physiological parameters than hamsters with low EIC receiving a single dose. alpha1-antitrypsin; disease models; lung mechanics; susceptibility

Chronic pancreatitis (CP) is a relatively common disorder, characterized by glandular insufficiency and chronic, often intractable, pain. The mechanism of pain in CP is poorly understood. We have previously developed a model of trinitrobenzene sulphonic acid (TNBS)-induced CP that results in nociceptive sensitization in rats. This study was designed to examine changes in the excitability and alteration of voltage-gated [K.sup.+] currents of dorsal root ganglia (DRG) neurons innervating the pancreas. CP was induced in adult rats by an intraductal injection of TNBS. DRG neurons innervating the pancreas were identified by 1,1'-dioleyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate fluorescence labeling. Perforated patch-clamp recordings were made from acutely dissociated DRG neurons from control and TNBS-treated rats. Pancreas-specific DRG neurons displayed more depolarized resting potentials in TNBS-treated rats than those in controls (P < 0.02). Some neurons from the TNBS-treated group exhibited spontaneous firings. TNBS-induced CP also resulted in a dramatic reduction in rheobase (P < 0.05) and a significant increase in the number of action potentials evoked at twice rheobase (P < 0.05). Under voltage-clamp conditions, neurons from both groups exhibited transient A-type ([I.sub.A]) and sustained outward rectifier [K.sup.+] currents ([I.sub.K]). Compared with controls, the average [I.sub.A] but not the average [I.sub.K] density was significantly reduced in the TNBS-treated group (P < 0.05). The steady-state inactivation curve for [I.sub.A] was displaced by ~20 mV to more hyperpolarized levels after the TNBS treatment. These data suggest that TNBS treatment increases the excitability of pancreas-specific DRG neurons by suppressing [I.sub.A] density, thus identifying for the first time a specific molecular mechanism underlying chronic visceral pain and sensitization in CP. dorsal root ganglion; inflammation; visceral pain; trinitrobenzene sulfonic acid; membrane properties doi:10.1152/ajpgi.00560.2005

Exposure to hypoxia induces anorexia in humans and rodents, but the role of leptin remains under discussion and that of orexigenic and anorexigenic hypothalamic neuropeptides remains unknown. The present study was designed to address this issue by using obese ([Lepr.sup.fa]/[Lepr.sup.fa]) Zucker rats, a rat model of genetic leptin receptor deficiency. Homozygous lean ([Lepr.sup.FA]/[Lepr.sup.FA]) and obese ([Lepr.sup.fa]/ [Lepr.sup.fa]) rats were randomly assigned to two groups, either kept at ambient pressure or exposed to hypobaric hypoxia for 1, 2, or 4 days (barometric pressure, 505 hPa). Food intake and body weight were recorded throughout the experiment. The expression of leptin and vascular endothelial growth factor (VEGF) genes was studied in adipose tissue with real-time quantitative PCR and that of selected orexigenic and anorexigenic neuropeptides was measured in the hypothalamus. Lean and obese rats exhibited a similar hypophagia (38 and 67% of initial values at day 1, respectively, P < 0.01) and initial decrease in body weight during hypoxia exposure. Hypoxia led to increased plasma leptin levels only in obese rats. This resulted from increased leptin gene expression in adipose tissue in response to hypoxia, in association with enhanced VEGF gene expression. Increased hypothalamic neuropeptide Y levels in lean rats 2 days after hypoxia exposure contributed to accounting for the enhanced food consumption. No significant changes occurred in the expression of other hypothalamic neuropeptides involved in the control of food intake. This study demonstrates unequivocally that altitude-induced anorexia cannot be ascribed to anorectic signals triggered by enhanced leptin production or alterations of hypothalamic neuropeptides involved in anabolic or catabolic pathways. altitude; anorexia; energy balance; adipose tissue

During 5,230 trapping nights, 672 small mammals were trapped in the areas where most hantavirus pulmonary syndrome (HPS) cases occur in Uruguay. Yellow pygmy rice rats (Oligoryzomys flavescens) were the [...]

This study examined environmental and physiological mediators of responses to hantavirus in wild-caught Norway rats. Rats were trapped in Baltimore, Maryland from 1996 to 2000, and prevalence of Seoul virus in target tissues, antibody responses against Seoul virus, concentrations of steroid hormones, and masses of reproductive organs were measured. Approximately 50% of live-trapped rats were infected with Seoul virus. No seasonal or photoperiodic changes in prevalence of Seoul virus infection or in antibody responses against Seoul virus were observed. Animals trapped during low temperatures had higher antibody responses than animals trapped during mild temperatures. Adults were more likely to have Seoul virus in kidneys and lungs and have higher antibody responses than juveniles. Older adult rats also were more likely to be infected and have higher antibody responses than younger adults. Rates of Seoul virus infection were similar between sexes; females, however, had higher anti-Seoul virus IgG responses than males. Although age- and season-related changes in concentrations of steroid hormones were observed, concentrations were not related to variation in infection by Seoul virus. Finally, the masses of reproductive organs increased with age, were responsive to environmental changes, and may be related to variation in Seoul virus infection. Thus, physiological and behavioral changes associated with sexual maturation may be the best predictors of Seoul virus infection in Norway rats, suggesting that metabolic trade-offs among growth, reproduction, and immune function occur at the onset of puberty. Key words: age, antibody, hantavirus, hormones, photoperiod, puberty, season, sex, steroids, temperature

The effect of a reduced number of nephrons from birth on arterial pressure in adulthood has been investigated. Sprague-Dawley rat pups were uninephrectomized during the first 24 hours after birth. Experimental results show that surgical removal of 50% of the nephrons, when performed during development, reduces renal function and a salt-sensitive hypertension in adulthood, indicating that a reduced nephron endowment from birth could result in hypertension in adulthood.

Experimental evidence shows that increased gastrointestinal permeability is present in spontaneously diabetic BB rats before development of autoimmune diabetes. This was gleaned from the results of a study which measured gastrointestinal permeability in rats fed with regular or hydrolyzed casein diet. It was found that increased gastric and small intestinal permeability arose before the onset of both insulitis and clinical diabetes.