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It is well recognized that serum creatinine level provides a quick general assessment of renal function. However, we frequently encounter elderly hypertensive patients with renal involvement whose serum creatinine levels are within normal limits. The aim of this study was thus to determine whether serum creatinine level is a sensitive indicator of renal function in elderly hypertensive patients. Study groups were classified according to age: 82 elderly patients (aged 65 yr or older) and 98 middle-aged patients (aged 40-65 yr) with essential hypertension. To assess hypertensive renal involvement, serum creatinine and serum uric acid levels were measured. We also measured the left ventricular mass (LVM) index by using echocardiography as a marker of hypertensive target organ damage. There was no age-related difference in the LVM index, but the serum creatinine level in elderly hypertensive patients was significantly lower than that in middle-aged hypertensive patients. There was no significant difference in serum uric acid level between the two groups. In addition, the LVM index was correlated with the serum uric acid level (r = 0.46, p = 0.0001) but not with the serum creatinine level in elderly hypertensive patients. In middle-aged hypertensive patients, the LVM index was related to both serum uric acid level (r = 0.41, p = 0.007) and serum creatinine level (r = 0.43, p = 0.003). In conclusion, serum creatinine level may underestimate hypertensive renal involvement in elderly hypertensive patients. In contrast, serum uric acid level may be a sensitive indicator of hypertensive target organ damage irrespective of age.

Objectives: To elucidate an association between left ventricular geometric adaptation to sustained hypertension and preclinical extracardiac target organ damage in essential hypertension. We also studied the clinical significance of neurohumoral factors for cardiovascular structural changes., Design: One hundred and forty patients with essential hypertension were divided into four subgroups, based on left ventricular mass index and relative wall thickness. With respect to extracardiac target organ damage, we measured the funduscopic grade of retinal changes and serum creatinine levels., Results: Among the hypertensive patients, only 19 (14%) had a typical concentric hypertrophy (increase in left ventricular mass index and relative wall thickness). Hypertensive patients with concentric hypertrophy had the most advanced funduscopic abnormalities and the greatest renal involvement, and hypertensive patients without left ventricular hypertrophy had the least extracardiac target organ damage. Plasma renin activity and plasma aldosterone concentration were higher in hypertensive patients with than in those without concentric hypertrophy. In a multiple regression model there was a strongly significant correlation between the degree of left ventricular mass index and the severity of hypertensive retinopathy and renal involvement, independent of office blood pressure., Conclusions: These results clearly demonstrate that echocardiographically determined left ventricular mass and geometry stratify extracardiac target organ damage in patients with essential hypertension more closely than office blood pressure. The present study also suggests that, in addition to blood pressure load, the renin-angiotensin-aldosterone system appears to play an important role in myocardial hypertrophy and peripheral vascular damage in hypertension.

To study the effect of antihypertensive therapy on the regulation of renin gene expression, the levels of tissue renin messenger RNA (mRNA) were measured after treatment with a calcium channel blocker (manidipine hydrochloride 3 mg/kg/day) or an angiotensin-converting enzyme inhibitor (delapril hydrochloride 30 mg/kg/day), administered orally for 1 week, in spontaneously hypertensive rats (SHR). Male SHR, aged 15 weeks old, were used in this study (n = 5 per group). Control rats were administered the vehicle alone. Tissue total RNA was isolated from kidney, adrenal gland, heart, and brain tissue, and tissue RNA was reverse-transcribed to complementary DNA (cDNA), which was specifically amplified by polymerase chain reaction with labeled-primers for the rat renin gene. The radioactivity of the cDNA products was measured directly. Although delapril increased plasma renin activity (PRA) about 5-fold compared with the control group, manidipine did not change PRA. The kidney renin mRNA content was increased about 6-fold by treatment with delapril. Manidipine and delapril significantly decreased the renin mRNA content in the heart (p < 0.01 and p < 0.05, respectively). The level of renin mRNA in the adrenal gland and brain tissues was not significantly changed by treatment with either drug. These results suggest that tissue renin gene expression in SHR is regulated by a tissue-specific process independent of the circulating renin-angiotensin system.

We investigated the effects of the human renin inhibitor, ES-8891, and captopril on renal renin secretion and storage in the marmoset. Either ES-8891 (30 mg/kg) or captopril (2 mg/kg) was given orally twice a day for 1 week to conscious, sodium-depleted marmosets (n = 6 for each group). The ES-8891-treated group displayed a significant reduction in mean arterial pressure (MAP), plasma renin activity (PRA) and plasma immunoreactive renin (PIR) compared with the control group. Kidney renin content was significantly increased compared with the control group and enlarged renin granules containing heterogenous internum were observed in juxtaglomerular cells after treatment with ES-8891. Treatment with captopril significantly increased PRA and PIR compared with the control day as well as increasing kidney renin content and the number of renin granules with crystalline content in juxtaglomerular cells compared with the control group. These results suggest that ES-8891 inhibits both PRA and renin secretion from the kidney, resulting in an increase in renal renin storage.

1. The effects of renin inhibitor ES-8891 on renin synthesis and its secretion by the kidney were investigated in normotensive sodium-depleted marmosets. We measured plasma renin activity, plasma immunoreactive renin concentration, plasma angiotensin II concentration and kidney renin mRNA content after oral administration of ES-8891 (60 mg day-1 kg-1) for 1 week. 2. The mean blood pressure was significantly decreased (P less than 0.01) on day 7 after oral administration of ES-8891. There was no significant change in heart rate during the administration. 3. Oral administration of ES-8891 for 1 week markedly decreased the plasma renin activity, the plasma immunoreactive renin concentration and the plasma angiotensin II concentration (to 18%, 41% and 24% of the corresponding control values; P less than 0.05 for each, n = 5). 4. The kidney renin mRNA content in ES-8891-treated marmosets was significantly lower than that in normal controls (4.2 +/- 3.5 versus 12.8 +/- 5.5 pg/micrograms of total RNA, means +/- SD, P less than 0.05, n = 5). 5. Oral administration of the renin inhibitor ES-8891 for 1 week not only inhibited plasma renin activity but also decreased renin synthesis and its secretion by the kidney.

Renal denervation has been shown to delay the onset of hypertension in spontaneously hypertensive rats and DOCA-salt sensitive rats. We investigated the contribution of the renal nerves to the development of hypertension in Dahl-Iwai salt-sensitive (DS) rats. Bilateral renal denervation or sham-operation was carried out in DS rats, and animals were then kept on a high salt diet (study I) or on a normal salt diet (study II). DS rats became severely hypertensive (207 +/- 8 mmHg) after 4 weeks on a high salt diet. They became mildly hypertensive (156 +/- 3 mmHg) after 4 weeks on a normal salt diet. In both studies, renal denervation exerted no effect on the development of hypertension in the DS rats. The urinary sodium excretion, urinary volume, heart rate and body weight were unaltered by renal denervation. These results indicate that the renal nerves do not make a major contribution to the development of hypertension in DS rats.

1. An in vitro experiment was carried out to compare the inhibitory effect of SQ29,852 on human renal angiotensin converting enzyme (ACE) with those of captopril, enalapril and enalaprilat. 2. SQ29,852 strongly inhibited human renal ACE; its IC50 value was 1.5 x 10(-8) M. In terms of the IC50, SQ29,852's efficacy was about 1/10 of that of captopril and 1/28 of that of enalaprilat, but it was about 14 times more potent than enalapril. 3. SQ29,852 showed no inhibitory effects on cathepsin D, urinary kallikrein, renal renin, pepsin, trypsin and chymotrypsin. Its ACE-specificity was higher than that of captopril. 4. ACE inhibition by SQ29,852 was shown to be competitive, as revealed by Lineweaver-Burk plots. The affinity of SQ29,852 to ACE was shown to be high by a Ki value of 1.2 x 10(-8) M.

Human membrane-bound neutral arylamidases were solubilized from small intestinal mucosa, lung, kidney, liver and placenta with trypsin. These five membrane-bound neutral arylamidases were identified by polyacrylamide gel-disc electrophoresis. The heat sensitivity of each enzyme was in the order, liver and placenta greater than kidney greater than lung greater than small intestine. This order correlates with that of electrophoretic mobility, except for the placental membrane-bound neutral arylamidase. Five membrane-bound neutral arylamidases have the same molecular weight, 240 000, as estimated by Sephadex G-200 gel filtration. The five membrane-bound neutral arylamidase have very similar KM values (8.7 x 10(-5) M towards L-alanyl-beta-naphthylamide), optimal pH values, hydrolysis ratios towards L-alanyl-beta-naphthylamide and L-leucyl-beta-naphthylamide, and sensitivities of inhibition by chelators or amino acids. These results suggest that the multiple forms of membrane-bound neutral arylamidase found in five different human organs are organ-specific isoenzymes.

Alkaline phosphatase (EC 3.1.3.1) from pig kidney brush-border membranes was solubilized from membrane precipitates by butan-1-ol at a critical pH of 7.0. The 12000-fold purification procedure included (NH(4))(2)SO(4) precipitation, DEAE-and TEAE-cellulose chromatography, Sephadex G-200 gel filtration and neuraminidase digestion followed by DEAE-cellulose chromatography. The purified protein contained 20% (w/w) carbohydrate and had mol.wt. 150000-156000 as estimated by Sephadex filtration and ultracentrifuge analysis. It was a tetrameric glycoprotein consisting of identical subunits, and it had a molecular activity at 25 degrees C of 2600s(-1) per tetramer. Its concentration in kidney was estimated to be 8.5-8.8mg/kg.

Experiments were performed to determine whether the renal nerve mediates the renin release induced by intracerebroventricular administration of angiotensin II (ANG II), bradykinin (BK), leucine-enkephalin (Leu-ENK) and neurotensin (NT). In sham-operated rats, both ANG II and NT suppressed plasma renin activity (PRA), BK did not affect PRA, and Leu-ENK increased PRA. Renal denervation abolished the increase in PRA by Leu-ENK. Suppression of PRA by ANG II was attenuated in denervated rats. Renal denervation did not influence the renin release by BK or NT. These results suggest that the renal nerve plays an important role in elevating PRA after central stimulation by Leu-ENK. Although suppression of PRA is mainly mediated by mechanisms other than the renal nerve, the renal nerve partially participates in suppression of PRA by ANG II.

Several alkaline phosphatases (EC 3.1.3.1) could be obtained from pig kidney brush-border membrane on extraction with butan-1-ol. Three of the multiple forms were separated by DEAE-cellulose chromatography and further purified. They form a regular series with different degrees of glycosylation (mainly owing to N-acetylneuraminic acid), of charge, of molecular weight, of stability to temperature, to pH and to urea, of minimal requirement for Mg(2+) and of extractability by butan-1-ol. In contrast, the detectable antigenic sites, the inhibition by amino acids and the pH-dependency of K(m) and V(max.) were identical for these multiple forms. On treatment with neuraminidase, the multiple forms became identical in all their properties. It was therefore concluded that the microheterogeneity of alkaline phosphatase is due to different degrees of glycosylation at polypeptide chains which appear to be otherwise identical.

The enzymic properties of alkaline phosphatase (EC 3.1.3.1) from pig kidney brush-border membranes were studied. 1. It hydrolyses ortho- and pyro-phosphate esters, the rate limiting step (V(max.)) being independent of the substrate. It transphosphorylates to Tris at concentrations above 0.1m-Tris. 2. The pH optimum for hydrolysis was between 9.8 and 10. The pK of the enzyme-substrate complex is 8.7 for p-nitrophenyl phosphate and beta-glycerophosphate. Excess of substrate inhibits the enzymic activity with decreasing pH. The pK of the substrate-inhibited enzyme-substrate complex, 8.7, is very similar to that for the enzyme-substrate complex. The pK values of the free enzyme appear to be 8.7 and 7.9. 3. Inactivation studies suggest that there is an essential tyrosine residue at the active centre of the enzyme. 4. The energy of activation (E) and the heat of activation (DeltaH) at pH9.5 showed a transition at 24.8 degrees C that was unaffected by Mg(2+). 5. Kinetic and atomic-absorption analysis indicated the essential role of two Zn(2+) ions/tetrameric enzyme for an ordered association of the monomers. Zn(2+) in excess and other bivalent ions compete for a second site with Mg(2+). Mg(2+) enhances only the rate-limiting step of substrate hydrolysis. 6. Amino acid inhibition studies classified the pig kidney enzyme as an intermediate type of previously described alkaline phosphatases. It has more similarity with the enzyme from liver and bone than with that from placenta.

A 53-year-old woman with nephroptosis and aortitis disease was found also to have orthostatic hypertension. When standing, she had high renin levels and normal catecholamine values, with a reduced baroreflex sensitivity. This orthostatic hypertension largely may be due to an activation of the renin system caused by nephroptosis and partly due to a reduced baroreflex sensitivity caused by aortitis. Captopril and propranolol hydrochloride were effective for the treatment of hypertension.

Membrane-bound arylamidases (EC 3.4.11.2) from human placenta and kidney were purified. The enzymes were solubilized from membrane fractions using trypsin. Purification procedures included DEAE-cellulose column chromatography, concanavalin-A--Sepharose 4B column chromatography, hydroxyapatite column chromatography and Sephadex G-200 gel filtration. The final recoveries of placental and kidney enzymes were 22.0% and 20.8% respectively. Polyacrylamide gel electrophoresis, analytical isoelectric focusing, immunoelectrophoresis and ultracentrifugation indicated the homogeneity of both purified enzymes. Equilibrium ultracentrifugation showed molecular weights of 193000 for placental enzyme and 211000 for kidney enzyme. Electrophoresis of the enzymes under denaturing conditions on dodecylsulfate/polyacrylamide gel indicated that each enzyme was a dimer consisting of two identical subunits. Isoelectric points of placental and kidney enzymes were 4.20 and 4.32 at 4 degrees C, respectively. The amino acid compositions of the two membrane-bound arylamidases were similar. The carbohydrate accounted for 18.2% of placental enzyme and 17.4% of kidney enzyme. The purified placental enzyme had a specific activity of 60.1 mumol min-1 (mg protein)-1 and the kidney enzyme had a specific activity of 96.4 mumol min-1 (mg protein)-1. Kcat values of placental and kidney enzymes were 187.8 s-1 and 328.6 s-1, respectively. The hydrolytic coefficient (Kcat/Km) of placental enzyme for L-alanyl-beta-naphthylamide was 2159 mM-1 s-1 and that of kidney enzyme was 3778 mM-1 s-1. Rabbit antibodies against placental and kidney membrane-bound arylamidases inhibited the activities of the corresponding antigens, but the inhibitions were never complete. Three membrane-bound arylamidases from placenta, kidney and renal cell carcinoma were immunochemically indistinguishable.

The effect of renin inhibitor ES-1005 on renin gene expression was investigated in sodium-depleted marmosets. The kidneys were removed after continuous infusion of ES-1005 (12 mg/kg per h) for 2 h. The relative amount of kidney renin messenger (m)RNA was measured by densitometric Northern blot analysis using an alpha-32P-labelled human renin complementary (c)DNA fragment as a hybridization probe. Plasma renin activity was completely inhibited by ES-1005. The level of kidney renin mRNA decreased significantly to about one-third of the normal control value. We also investigated the inhibitory potency of the renin inhibitor ES-6864 on the renin-like activity in dog tissues (adrenal glands, aorta and brainstem). ES-6864 inhibited the tissue renin-like activity with an IC50 of 10(-7) to 10(-8) mol/l in vitro. Renin inhibitors not only inhibit the activity of plasma and tissue renin, but also suppress the synthesis of renin in the kidney.

We studied the expression of kidney renin gene in hypertensive animals by measuring the kidney renin messenger (m) RNA. The kidney renin mRNA was quantified by densitometric Northern blot analysis using a 32P-labelled rat renin genomic DNA fragment as a hybridization probe. Spontaneously hypertensive rats (SHR) and control Wistar-Kyoto rats (WKY) were treated with a low-sodium diet plus furosemide, captopril or propranolol for a week. Plasma renin activity (PRA) in SHR and WKY was increased similarly by sodium depletion and by treatment with captopril. PRA in both strains was not decreased significantly by treatment with propranolol. Both sodium depletion and captopril treatment caused significant increases in the kidney renin mRNA in SHR and WKY. However, the increases in the kidney renin mRNA of SHR were greater than those in the corresponding WKY (SHR, 10.0- and 22.1-fold increases; WKY, 6.2- and 7.8-fold increases, respectively). Propranolol had no effect on the kidney renin gene expression in either WKY or SHR. These results indicate that SHR show an enhanced expression of the renin gene in the kidney compared with WKY in response to stimuli that increase renin release.