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ABSTRACTIntroductionAutomated patch clamp (APC) is now well established as a mature technology for ion channel drug discovery in academia, biotech and pharma companies, and in contract research organizations (CRO), for a variety of applications including channelopathy research, compound screening, target validation and cardiac safety testing.Areas coveredIon channels are an important class of drugged and approved drug targets. The authors present a review of the current state of ion channel drug discovery along with new and exciting developments in ion channel research involving APC. This includes topics such as native and iPSC-derived cells in ion channel drug discovery, channelopathy research, organellar and biologics in ion channel drug discovery.Expert opinionIt is our belief that APC will continue to play a critical role in ion channel drug discovery, not only in ‘classical’ hit screening, target validation and cardiac safety testing, but extending these applications to include high throughput organellar recordings and optogenetics. In this way, with advancements in APC capabilities and applications, together with high resolution cryo-EM structures, ion channel drug discovery will be re-invigorated, leading to a growing list of ion channel ligands in clinical development.

Assessment of Peyronie’s disease with penile injection is invasive and uncomfortable. We developed a smartphone application (UWPEN) to assess penile angulation in the home environment. The purpose of this study was to compare clinician and patient measurements and assess the patient experience with UWPEN in a clinical setting. We prospectively enrolled patients with Peyronie’s disease undergoing intracavernosal injection of alprostadil. Penile angulation and narrowing were then assessed by patients and clinicians using UWPEN and compared to values obtained via a goniometer and a ruler (gold standard). Measurements were compared using the Pearson correlation test. Upon completion of measurements, patients were surveyed regarding the ease of use, confidence with use, and measurement preferences. Twenty patients were enrolled in the study; two patients were excluded for poor penile turgidity after a maximum dosage of intracavernosal alprostadil. Correlation between UWPEN and gold standard measurements by patients and clinicians was R= 0.55 (p= 0.01) and R= 0.87 (p< 0.01) for dorsal measurements, R= 0.62 (p= 0.01) and R= 0.77 (p< 0.01) for lateral measurements, and R= 0.73 (p< 0.01) and R= 0.64 (p< 0.01) for girth measurements, respectively. Prior evaluation of correlation suggests a strong correlation at R= 0.8, and good correlation at R= 0.5. Overall, patients preferred using UWPEN to traditional measurements, and 75% reported UWPEN as their first preference for measurements. UWPEN enables patients to assess their disease severity with good correlation to gold standard measurements. Patients prefer mobile platforms for disease monitoring, and development of technology for disease monitoring should be a priority within the Peyronie’s disease research community.

This study examined the role of spinal metabotropic glutamate receptor 5 (mGluR5) in the nociceptive C-fiber afferent-mediated spinal bladder reflex and in the inhibtion of this reflex by pudendal nerve stimulation (PNS). In α-chloralose-anesthetized cats after spinal cord transection at the T9/T10 level, intravesical infusion of 0.25% acetic acid irritated the bladder, activated nociceptive C-fiber afferents, and induced spinal reflex bladder contractions of low amplitude (<50 cmH2O) and short duration (<20 s) at a smaller bladder capacity ∼80% of saline control capacity. PNS significantly (P< 0.01) increased bladder capacity from 85.5 ± 10.1 to 137.3 ± 14.1 or 148.2 ± 11.2% at 2T or 4T stimulation, respectively, where T is the threshold intensity for PNS to induce anal twitch. MTEP {3-[(2-methyl-4-thiazolyl)ethynyl]pyridine; 3 mg/kg iv, a selective mGluR5 antagonist} completely removed the PNS inhibition and significantly (P< 0.05) increased bladder capacity from 71.8 ± 9.9 to 94.0 ± 13.9% of saline control, but it did not change the bladder contraction amplitude. After propranolol (3 mg/kg iv, a β1/β2-adrenergic receptor antagonist) treatment, PNS inhibition remained but MTEP significantly (P< 0.05) reduced the bladder contraction amplitude from 18.6 ± 2.1 to 6.6 ± 1.2 cmH2O and eliminated PNS inhibition. At the end of experiments, hexamethonium (10 mg/kg iv, a ganglionic blocker) significantly (P< 0.05) reduced the bladder contraction amplitude from 20.9 ± 3.2 to 8.1 ± 1.5 cmH2O on average demonstrating that spinal reflexes were responsible for a major component of the contractions. This study shows that spinal mGluR5 plays an important role in the nociceptive C-fiber afferent-mediated spinal bladder reflex and in pudendal inhibition of this spinal reflex.

The goal of the present study was to determine if supraspinal pathways are necessary for inhibition of bladder reflex activity induced by activation of somatic afferents in the pudendal or tibial nerve. Cats anesthetized with α-chloralose were studied after acute spinal cord transection at the thoracic T9/T10 level. Dilute (0.25%) acetic acid was used to irritate the bladder, activate nociceptive afferent C-fibers, and trigger spinal reflex bladder contractions (amplitude: 19.3 ± 2.9 cmH2O). Hexamethonium (a ganglionic blocker, intravenously) significantly (P< 0.01) reduced the amplitude of the reflex bladder contractions to 8.5 ± 1.9 cmH2O. Injection of lidocaine (2%, 1–2 ml) into the sacral spinal cord or transection of the sacral spinal roots and spinal cord further reduced the contraction amplitude to 4.2 ± 1.3 cmH2O. Pudendal nerve stimulation (PNS) at frequencies of 0.5–5 Hz and 40 Hz but not at 10–20 Hz inhibited reflex bladder contractions, whereas tibial nerve stimulation (TNS) failed to inhibit bladder contractions at all tested frequencies (0.5–40 Hz). These results indicate that PNS inhibition of nociceptive afferent C-fiber-mediated spinal reflex bladder contractions can occur at the spinal level in the absence of supraspinal pathways, but TNS inhibition requires supraspinal pathways. In addition, this study shows, for the first time, that after acute spinal cord transection reflex bladder contractions can be triggered by activating nociceptive bladder afferent C-fibers using acetic acid irritation. Understanding the sites of action for PNS or TNS inhibition is important for the clinical application of pudendal or tibial neuromodulation to treat bladder dysfunctions.

The human electrophysiological and pharmacological properties of XEN-D0101 were evaluated to assess its usefulness for treating atrial fibrillation (AF). XEN-D0101 inhibited Kv1.5 with an IC50of 241 nM and is selective over non-target cardiac ion channels (IC50Kv4.3, 4.2 M; hERG, 13 M; activated Nav1.5, >100 M; inactivated Nav1.5, 34 M; Kir3.13.4, 17 M; Kir2.1, >>100 M). In atrial myocytes from patients in sinus rhythm (SR) and chronic AF, XEN-D0101 inhibited non-inactivating outward currents (Ilate) with IC50of 410 and 280 nM, respectively, and peak outward currents (Ipeak) with IC50of 806 and 240 nM, respectively. Whereas Ilateis mainly composed of IKur, Ipeakconsists of IKurand Ito. Therefore, the effects on Itoalone were estimated from a double-pulse protocol where IKurwas inactivated (3.5 µM IC50in SR and 1 µM in AF). Thus, inhibition of Ipeakis because of IKurreduction and not Ito. XEN-D0101 significantly prolonged the atrial action potential duration at 20, 50, and 90 of repolarization (AF tissue only) and significantly elevated the atrial action potential plateau phase and increased contractility (SR and AF tissues) while having no effect on human ventricular action potentials. In healthy volunteers, XEN-D0101 did not significantly increase baseline- and placebo-adjusted QTc up to a maximum oral dose of 300 mg. XEN-D0101 is a Kv1.5IKurinhibitor with an attractive atrial-selective profile.

Background: Prescription costs for treatment of comorbidities associated with morbid obesity is a considerable annual health-care expenditure. This study addressed the effect of Roux-en-Y gastric bypass (RYGBP) on diabetic and anti-hypertensive pharmaceutical utilization and cost savings at our institution. Methods: Retrospective data from the electronic database of 51 consecutive patients, who underwent RYGBP from March 2001 to May 2002 were studied. Patients had BMI >40 associated with obesity-related diabetes and hypertension. Prescription medications utilized by this cohort were reviewed preoperatively and at 3- and 9-month intervals postoperatively. Significance was analyzed by paired t-test. Results: Prevalence of diabetes and hypertension was 55.7% (29/53) and 44.3% (24/53) respectively, and 34% (18/53) patients had both co-morbidities. Preoperatively, patients were on an average of 2.44 � 1.86 medications at a cost of $187.24 � $237.41 per month. Postoperatively, the mean number of medications was reduced to 0.56 � 0.81 agents (P<0.001) at a monthly cost of $42.53 � 116.60 (P<0.001). Conclusions: RYGBP can decrease the prescription medication requirements, resulting in significant cost-savings in the treatment of obesity-related hypertension and diabetes. This study found a 77.3% reduction in total cost of diabetic and anti-hypertensive medications.

This study examined changes in myostatin gene expression in response to strength training (ST). Fifteen young and older men (n= 7) and women (n= 8) completed a 9-week heavy-resistance unilateral knee extension ST program. Muscle biopsies were obtained from the dominant vastus lateralis before and after ST. In addition to myostatin mRNA levels, muscle volume and strength were measured. Total RNA was reverse transcribed into cDNA, and myostatin mRNA was quantified using quantitative PCR by standard fluorescent chemistries and was normalized to 18S rRNA levels. A 37% decrease in myostatin expression was observed in response to ST in all subjects combined (2.70 ± 0.36 vs 1.69 ± 0.18 U, arbitrary units; P< 0.05). Though the decline in myostatin expression was similar regardless of age or gender, the small number of subjects in these subgroups suggests that this observation needs to be confirmed. No significant correlations were observed between myostatin expression and any muscle strength or volume measure. Although further work is necessary to clarify the findings, these data demonstrate that myostatin mRNA levels are reduced in response to heavy-resistance ST in humans.

The purpose of this study was to determine the influence of age, sex, and strength training (ST) on large-scale gene expression patterns in vastus lateralis muscle biopsies using high-density cDNA microarrays and quantitative PCR. Muscle samples from sedentary young (20–30 yr) and older (65–75 yr) men and women (5 per group) were obtained before and after a 9-wk unilateral heavy resistance ST program. RNA was hybridized to cDNA filter microarrays representing ∼4,000 known human genes and comparisons were made among arrays to determine differential gene expression as a result of age and sex differences, and/or response to ST. Sex had the strongest influence on muscle gene expression, with differential expression (>1.7-fold) observed for ∼200 genes between men and women (∼75% with higher expression in men). Age contributed to differential expression as well, as ∼50 genes were identified as differentially expressed (>1.7-fold) in relation to age, representing structural, metabolic, and regulatory gene classes. Sixty-nine genes were identified as being differentially expressed (>1.7-fold) in all groups in response to ST, and the majority of these were downregulated. Quantitative PCR was employed to validate expression levels for caldesmon, SWI/SNF (BAF60b), and four-and-a-half LIM domains 1. These significant differences suggest that in the analysis of skeletal muscle gene expression issues of sex, age, and habitual physical activity must be addressed, with sex being the most critical variable.

The purpose of the present investigation was to assess satellite cell populations and morphology in m. vastus lateralis biopsies obtained from young (20–30 years) and older (65–75 years) healthy, sedentary men and women. Multiple muscle biopsies were obtained from 14 young individuals (men, n = 7; women, n = 7) and 15 older individuals (men, n = 8; women, n = 7). Muscle fibers were viewed longitudinally using a Zeiss EM 10 CA electron microscope. All myonuclei and satellite cells were counted and satellite cells were photographed for morphological analysis. The proportion of satellite cells [satellite cells/(myonuclei + satellite cells)] did not differ among the four subject groups (1.7–2.8%), nor did proportions differ when subject groups were combined for age and gender comparisons. Few morphological differences were noted between groups; however, lipofuscin granules were more prominent in satellite cells from older subjects and women demonstrated significantly larger satellite cell and satellite cell nucleus areas than men. Mitochondria from satellite cells (regardless of group) were more pallid and exhibited fewer cristae than mitochondria located in the adjacent muscle fiber. The results of the current investigation suggest that, despite findings in animal models, satellite cell populations are not significantly lower in healthy, sedentary older compared to young adult men and women. Anat Rec 260:351–358, 2000. © 2000 Wiley‐Liss, Inc.

The purpose of the present investigation was to assess satellite cell populations and morphology in m. vastus lateralis biopsies obtained from young (20–30 years) and older (65–75 years) healthy, sedentary men and women. Multiple muscle biopsies were obtained from 14 young individuals (men, n = 7; women, n = 7) and 15 older individuals (men, n = 8; women, n = 7). Muscle fibers were viewed longitudinally using a Zeiss EM 10 CA electron microscope. All myonuclei and satellite cells were counted and satellite cells were photographed for morphological analysis. The proportion of satellite cells [satellite cells/(myonuclei + satellite cells)] did not differ among the four subject groups (1.7–2.8%), nor did proportions differ when subject groups were combined for age and gender comparisons. Few morphological differences were noted between groups; however, lipofuscin granules were more prominent in satellite cells from older subjects and women demonstrated significantly larger satellite cell and satellite cell nucleus areas than men. Mitochondria from satellite cells (regardless of group) were more pallid and exhibited fewer cristae than mitochondria located in the adjacent muscle fiber. The results of the current investigation suggest that, despite findings in animal models, satellite cell populations are not significantly lower in healthy, sedentary older compared to young adult men and women. Anat Rec 260:351–358, 2000. © 2000 Wiley-Liss, Inc.

To determine possible age differences in muscle damage response to strength training, ultrastructural muscle damage was assessed in seven 20- to 30-yr-old and six 65- to 75-yr-old previously sedentary women after heavy-resistance strength training (HRST). Subjects performed unilateral knee-extension exercise 3 days/wk for 9 wk. Bilateral muscle biopsies from the vastus lateralis were assessed for muscle damage via electron microscopy. HRST resulted in a 38 and 25% increase in strength in the young and older women, respectively (P< 0.05), but there were no between-group differences. In the young women, 2–4% of muscle fibers exhibited damage before and after training in both the trained and untrained legs (P= not significant). In contrast, muscle damage increased significantly after HRST, from 5 to 17% of fibers damaged (P< 0.01), in the older women in the trained leg compared with only 2 and 5% of fibers damaged in the untrained leg before and after training, respectively. The present results indicate that older women exhibit higher levels of muscle damage after chronic HRST than do young women.

This study assessed ultrastructural muscle damage in young (20–30 yr old) vs. older (65–75 yr old) men after heavy-resistance strength training (HRST). Seven young and eight older subjects completed 9 wk of unilateral leg extension HRST. Five sets of 5–20 repetitions were performed 3 days/wk with variable resistance designed to subject the muscle to near-maximal loads during every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training resulted in a 27% strength increase in both groups (P< 0.05). In biopsies before training in the trained leg and in all biopsies from untrained leg, 0–3% of muscle fibers exhibited muscle damage in both groups (P= not significant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage in the young and older men, respectively (P< 0.05, no significant group differences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST.

Total creatine kinase (CK) and CK MB activities were determined in gastrocnemius muscle and serum obtained from 14 female marathon runners. The level of CK MB in muscle increased significantly (p<0.05) after chronic exercise training from 5.3% to 10.5% of the total CK activity, but not after acute exercise (post-marathon 8.9%). No significant differences in total CK activities were detected. However, the total CK activity in the muscles were significantly (p<0.05) less than those previously reported from the muscle of men runners (1800 U/g, 3000 U/g respectively). No significant correlation existed between fiber type and muscle CK MB activity. Additionally, trace amounts of mitochondrial CK and CK BB were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (597 UL-1) and CK MB (23 UL-1) activities 24 h after the race (r=0.97,P<0.05). These results suggest that gastrocnemius muscle in women adapts to training with increased CK MB activities and imply that skeletal muscle is the major source of elevated serum CK MB activities in women marathon runners.

The purpose of this study was to evaluate the effects of long-term exercise training on maximal aerobic exercise capacity, evidence of myocardial ischemia and plasma lipid-lipoprotein concentrations in patients with coronary artery disease. Nine men with coronary artery disease, aged 57 ± 2 years, who had completed 12 months of supervised intense exercise training were restudied after 6 additional years during which they continued to exercise. The first 12 months of training resulted in a 44% increase in maximal oxygen consumption ( VO2max) from 25.0 ± 1.3 to 35.9 ± 1.5 ml kg−1min−1(p < 0.001). The VO2max after 6 additional years (total 7 years) of intense training was 36.8 ± 2.4ml·kg−1min−1.

Serum samples from 14 men and 8 women were obtained pre-marathon (48 h) and at 24, 48, 72, and 96 h post-race to quantitate total serum creatine kinase activity (TCK), percentage of creatine kinase MB (CK-MB), and clearance rates (half-lives) of TCK. and CK-MB. TCK was measured enzymatically, and the CK-MB isoenzyme was separated by agarose electrophoresis and quantitated by densitometry. The men's and women's post-race mean TCK levels were significantly elevated P<0.05) above pre-race values at 24 h (3322 U.l-1, 946 U.lS-1) and 48 h (1787 U.l-1, 508 U.l-1). In addition, CK-MB was significantly elevated both 24 h (5.1 , 3.3) and 48 h (2.5, 1.8) post-race (P<0.05). The men's 24-h TCK was 22.3 times the prerace value, while the women had an 8.6-fold increase in TCK. The mean 24-h post-race CK-MB activities were 166 U.l-1for the men and 31 U.l-1for the women. The mean increase in CK-MB activity was 41.5-fold for the men and 7.8-fold for the women. Furthermore, the men had a mean half-life (t½) of 30.4 h for TCK and 12.0 h for CK-MB; the women's t½were 29.4 and 16.8 h, respectively. At all time points, the men evidenced significantly (P<0.05) higher TCK and CK-MB enzyme activities than did the women. The data indicate that men and women respond to the stress of marathon running with similar patterns of enzyme release, elevation, and clearance. The difference in absolute enzyme activities may be attributed to greater skeletal muscle damage of the larger muscle mass of men vs women.

Nine sedentary men (53 ± 3 yr) were studied before and after 6 d of endurance exercise training to determine the effects on maximal oxygen uptake (VO2 max), and on the heart rate, blood pressure, and metabolic responses to a standard bout of steady-state sub-maximal exercise. The subjects exercised approximately 1 h-d-1at about 68 of VO2 max. The 6-d protocol elicited no improvement in VO2 max, (2.50 ± 0.14 before vs 2.58 ± 0.15 1-min-1after training). Heart rates were significantly lower by 5 to 8 b-min-1, systolic blood pressures were reduced by 16 to 19 mm Hg, and blood lactate concentrations were 25 to 35 less at the same exercise intensities (60, 70, and 80 of VO2 max) after 6 d of exercise. Rate pressure product was about 15 lower at the same exercise intensity after 6 d of training (P<0.05). The respiratory exchange ratio during submaximal exercise was 0.02 to 0.04 units lower (P<0.05; P<0.01) after 6 d of exercise, indicating a shift in substrate utilization favoring fat oxidation. These findings suggest that short-term endurance training can induce heart rate, blood pressure, and metabolic adaptations to sub-maximal exercise before there is a significant increase in VO2 maxin sedentary, middle-aged men who are capable of vigorous exercise.

DeSouza, Christopher A., Donald R. Dengel, Marc A. Rogers, Kim Cox, and Richard F. Macko. Fibrinolytic responses to acute physical activity in older hypertensive men.J. Appl. Physiol.82(6): 1765–1770, 1997.—We tested the hypothesis that the fibrinolytic response to acute physical activity is impaired in sedentary older hypertensive men, which may contribute to the risk of exertion-triggered acute myocardial infarction in this population. Tissue-type plasminogen activator (t-PA) antigen and activity and plasminogen activator inhibitor-1 (PAI-1) antigen and activity were measured in 12 hypertensive (69 ± 1 yr) and 11 normotensive (64 ± 1 yr) men before and after an acute bout of submaximal exercise. Contrary to our hypothesis, there were no differences between the two groups in the fibrinolytic response to exercise. t-PA antigen and activity were significantly elevated in both the hypertensive (38 and 172%, respectively) and normotensive (45 and 130%, respectively) groups immediately after exercise but they returned to resting levels within 30 min. There was no change in PAI-1 antigen levels immediately after exercise in either group; however, PAI-1 antigen was significantly lower at 30 and 60 min postexercise in both the hypertensive (31 and 16%, respectively) and normotensive (35 and 20%, respectively) groups. PAI-1 activity was significantly lower immediately after exercise in both the hypertensive (25%) and normotensive (22%) groups and remained lower than preexercise levels at 30 min (23 and 26%, respectively) and 60 min (16 and 12%, respectively) postexercise in both groups. The results of this study demonstrate that the fibrinolytic response to an acute bout of moderate physical activity is not impaired in sedentary older hypertensive men.

Despite the widespread dissemination of information concerning the negative health consequences associated with sedentary living, adult physical activity in many industrialised nations remains well below recommended levels. Approximately 50% of individuals who start an aerobic exercise programme will stop within the first 6 months, even though it is well known that to obtain the health benefits associated with physical activity, participation must be maintained. Programmes involving the use of behaviour management techniques appear to increase short term adherence to exercise. Recently, an adherence rate of greater than 95% over 6 months was achieved in a large group of university employees who participated in aerobic training using a ‘behavioural treatment packages’ approach. Unfortunately, inconsistencies in the literature on definitions and measurement of adherence make valid comparisons among studies difficult. Also, long term follow-up of behavioural intervention methods and their effect on exercise adherence is generally lacking. It is likely that strategies to increase physical activity participation in the general population will demand multiple levels of intervention (personal, organisational, environmental and societal) if they are to succeed in the long term.

Twenty young men trained the right knee extensors and flexors on an isokinetic dynamometer three times weekly over a 10-week period. During each session, 10 men in the slow training group completed three sets of 8 maximal contractions at a rate of 1.05 rad s-1, whereas the other 10, the fast group, completed three sets of 20 contractions at a rate of 4.19 rad s-1. Subjects were pre- and post-tested for peak torque and power on an isokinetic dynamometer at 1.05, 3.14, and 4.19 rad s-1. Proportions of muscle fibre-types and fibre cross-sectional areas were determined from biopsy specimens taken before and after training from the right vastus lateralis. When testing was conducted at 1.05 rad s-1, the slow group improved (P<0.05) peak torque by 24.5 N m (8.5%), but no change was noted for the fast group. Power increased (P< 0.05) by 32.7 W (13.6%) in the slow group and 5.5 W (2.5%) in the fast. At 3.14 rad s-1, both groups increased (P<0.05) peak torque and power. At 4.19 rad s-1, the fast group increased (P<0.05) peak torque by 30.0 N m (19.7%), whereas no training effect was observed in the slow group. There was no significant change in power in either group at 4.19 rad s-1, No significant changes were observed over the 10-week training period in percentages of type I, IIa and IIb fibres, but both groups showed significant increases (P<0.05) in type I and IIa fibre areas. No differences were noted between groups, and no hypertrophy of type IIb fibres was observed.

We describe a program model designed to achieve high adherence, a major problem for work-site exercise/fitness programs. Our model is a 6-month program consisting of 15 1-hour program meetings, with participants exercising on their own time four times per week. Procedures employed to enhance adherence are contracting, group competition, monitoring, and social support. This program model has been applied nine times. One hundred fifty-nine university employees took part in the initial test with a dropout rate of 9 (15 persons). The average adherence rate for nondropouts was 98, which is higher than rates usually reported in the literature. Adherence was defined as exercising four times a week.

Sixteen untrained males (23 ± 4 yr), were studied to determine the effects of chromium (Cr) supplementation (200 μg · d-1) and a 12-wk resistive exercise training program on muscle strength, body composition, and Cr excretion. The subjects trained 3 times per week with two sets of 8-10 repetitions at 90% of 1 repetition maximum using Keiser variable resistance machines. Food records were used to estimate Cr intake (36μg · d-1), energy intake, and the percent kJ from protein. The resistive training program resulted in significant increases in total body muscular strength in both the Cr and placebo groups (24% and 33%; P< 0.05). Body weight, percent body fat, lean body mass, and skinfold thicknesses were unchanged in either group after resistive training. Cr excretion increased in the Cr group after 6 wk of Cr supplementation (0.15± 0.08 vs 1.52 ± 1.26 μg · d-1; P< 0.01) and remained higher at 12 wk of training (2.03 ± 1.73). These results indicate that Cr supplementation, in conjunction with a progressive, resistive exercise training program, does not promote a significant increase in strength and lean body mass, or a significant decrease in percent body fat. Cr supplementation results in a significant increase in Cr excretion that is not altered by resistive training.

Noradrenaline effects on voltage‐operated calcium channels and exocytosis were studied, for the first time, in single patch‐clamped RINm5F insulin‐secreting cells. Noradrenaline, despite small and variable inhibition of calcium currents, strongly inhibited the increase in membrane capacitance (a measure of exocytosis) stimulated by both step depolarizations and the calcium ionophore, ionomycin. Noradrenaline similarly inhibited KCl‐ and ionomycin‐induced [3H]serotonin release from RINm5F cell populations. Noradrenaline effects were mediated by PTX‐sensitive G proteins. Noradrenaline inhibitory effects on secretion are, therefore, mainly exerted downstream from Ca2+influx.

This study investigated exercise-induced muscle enzyme release in master runners by assessing the activity of total serum creatine kinase (total CK) and the concentration of the isoenzyme creatine kinase MB (CK-MB). Subjects were 12 male (54 ± 9 years) and seven female (50 ± 6 years) master marathon runners. Premarathon (24 hours before) and postmarathon serum samples were collected (24, 48, 72, and 96 hours after the race). Total CK was measured enzymatically and CK-MB concentration was assayed utilizing a double antibody procedure. The men's and women's 24 hour (1012 U/L, 782 U/L) and 48 hour (581 U/L, 441 U/L) postrace mean total CK activities were significantly (p≤0.05) elevated above prerace values (66 U/L, 119 U/L). CK-MB concentration 24 hours postrace was also significantly (≤0.05) elevated from prerace values (0.27 ng/ml, 0.0 ng/ml) in both males (34.4 ng/ml) and females (16.7 ng/ml). The results of this study indicate that the pattern of exercise-induced muscle enzyme release from the stress of endurance running in older runners was similar to the response in young runners. The magnitude of the elevation of serum enzyme activity in the master runners, however, was greater. This could indicate that marathon running places excessive stress on a muscular system already declining due to the aging process. Additionally, female runners had a much smaller increase than the male runners in total CK and CK-MB from prerace to 24 hours postrace, which was similar to the response in male and female young runners.

The evidence that exercise reduces resistance to the action of insulin has generated interest in the possibility that endurance exercise training may be a worthwhile primary therapeutic intervention in the treatment of mild non-insulin-dependent diabetes mellitus (NIDDM) (11). Unfortunately, the results of several studies of exercise training in NIDDM have been discouraging since improvements in oral glucose tolerance (OGT) did not occur or were quite modest even though insulin resistance was reduced. Recently it was determined that 12 months of endurance exercise training at 75–90 of o2maxcould normalize OGT in men with mild NIDDM when the post-training OGTT was performed within 18 h of the last bout of exercise. This, coupled with the fact that the enhanced action of insulin is lost in trained persons within a few days of cessation of training, suggests that improved glucose tolerance in NIDDM patients may be partly due to the persistent effects of the last bouts of exercise. Acute exercise in the form of 7 d of intense walking/cycling has been shown to improve glucose tolerance despite a significantly smaller increase in plasma insulin levels during the OGTT in NIDDM. Apparently, the improvement in OGT was due to a decrease in resistance to insulin over the short term since no changes in body weight, body fat, or o2maxtook place. Thus, acute exercise of sufficient intensity and duration can increase peripheral insulin action and may contribute to the effects of long-term exercise training on improvement in OGT and the amelioration of insulin resistance in patients with NIDDM.

Rogers, Marc, Lorna M. Colquhoun, James W. Patrick, and John A. Dani.Calcium flux through predominantly independent purinergic ATP and nicotinic acetylcholine receptors. J. Neurophysiol.77: 1407–1417, 1997. Ligand-gated nicotinic acetylcholine receptors (nAChRs) and purinergic ATP receptors are often expressed in the same peripheral and central neurons, and ATP and acetylcholine (ACh) are stored together in some synaptic vesicles. Evidence has suggested that nAChRs and ATP receptors are not independent and that some agonists strongly cross-activate and desensitize both receptor types. Rat sympathetic neurons and nAChRs expressed in Xenopusoocytes were studied to determine the significance of the interactions caused by the two agonist types. Current amplitudes induced with separate or combined applications of ATP and nicotine are >90% additive and independent. Half of all neurons tested responded to either ATP or nicotine but not to both, indicating differences in the expression of the two receptors. In neurons that expressed both receptor types, the nAChRs were inhibited by the activity-dependent open-channel blocker chlorisondamine. If the purinergic and nicotinic receptors were significantly dependent and coactivated, then blocking the ion channels opened by a nicotinic agonist should diminish the current activated by a purinergic agonist. That result was not seen; rather, complete open-channel block of nAChRs with chlorisondamine did not significantly alter the amplitude or kinetics of ATP-induced currents in the same neurons. Finally, when cloned nAChR subunits were expressed in oocytes, ATP activated only very small currents compared with the current activated by ACh. For the 13 different nAChR subunit combinations that were studied, ATP (50–500 μM) activated a current that ranged from 0 to 4% of the size of the current activated by 100 μM ACh. In summary, we find that there is little cross reactivity, and nAChRs and purinergic ATP receptors are predominately independent, acting with separable physiological characteristics. Therefore the quantitative Ca2+flux could be separately determined for nAChRs and ATP receptors. The fraction of total current that is carried by Ca2+was quantitatively determined by simultaneously measuring the whole cell current and the associated change in intracellular Ca2+with fura-2. For sympathetic neurons bathed in 2.5 mM Ca2+at a holding potential of −50 mV, Ca2+carries 4.8 ± 0.3% (mean ± SE) of the inward current through neuronal nAChRs and 6.5 ± 0.1% of the current through purinergic ATP receptors. In conclusion, activity-dependent Ca2+influx through predominately independent populations of nAChRs and ATP receptors can produce different intracellular signals at purinergic and cholinergic synapses.

To the Editor.—Marathon running has been shown to induce a variety of chemical changes in runners' serum.1 In the clinical laboratory, increases in serum alanine aminotransferase (ALT) activity have been shown to be very hepatospecific.2 Also, it has been suggested that ALT testing is potentially useful for screening blood donors to reduce incidence of non-A, non-B viral hepatitis.3,4 This report describes the changes in skeletal muscle and serum ALT activities in runners before and after a marathon race and discusses the potential for false biochemical indices for liver damage.Serum was obtained from 22 male (aged 21 to 36 years) and eight female (aged 24 to 35 years) runners two days before and 24, 48, 72, and 96 hours after a marathon race (26.2 miles). Gastrocnemius muscle biopsy specimens were obtained nine weeks before, two days before, and one day after the race from 14 male