Biomedical subjects

I L Kanstrup

Publications and source records attributed to I L Kanstrup.

At least 37 records · Page 2Linked to original sources

PubMed1998

Isokinetic eccentric exercise as a model to induce and reproduce pathophysiological alterations related to delayed onset muscle soreness.

Physiological alterations following unaccustomed eccentric exercise in an isokinetic dynamometer of the right m. quadriceps until exhaustion were studied, in order to create a model in which the physiological responses to physiotherapy could be measured. In experiment I (exp. I), seven selected parameters were measured bilaterally in 7 healthy subjects at day 0 as a control value. Then after a standardized bout of eccentric exercise the same parameters were measured daily for the following 7 d (test values). The measured parameters were: the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), the ratio of inorganic phosphate to adenosintriphosphate (Pi/ATP), the ratio of phosphocreatine to adenosintriphosphate (PCr/ATP) (all three ratios measured with 31P-nuclear magnetic resonance spectroscopy), dynamic muscle strength, plasma creatine kinase (CK), degree of pain and "muscle" blood flow rate (133Xenon washout technique). This was repeated in experiment II (exp. II) 6-12 months later in order to study reproducibility. In experiment III (exp. III), the normal fluctuations over 8 d of the seven parameters were measured, without intervention with eccentric exercise in 6 other subjects. All subjects experienced pain, reaching a maximum 48 h after eccentric exercise in both exp. I and II. A systematic effect over time for CK (increasing 278% resp. 308%), muscle strength (decreasing more than 10%), PCr/Pi (decreasing 31% resp. 43%) and Pi/ATP (increasing 55% resp. 99%) was found in both exp. I and II (P < 0.05), but not in exp. III. No significant difference was observed between exp. I and II for CK, blood-flow rate, concentric muscle strength, PCr/Pi, Pi/ATP and PCr/ATP. It is concluded that pathophysiological alterations in m. quadriceps following eccentric exercise can be induced and can be reproduced after an interval of 6 months. Thus, this model can be used to study the effects of physiotherapy.

Adenosine Triphosphate↗

PubMed1998

The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise.

The aim of this study was to measure if passive stretching would influence delayed onset muscle soreness (DOMS), dynamic muscle strength, plasma creatine kinase concentration (CK) and the ratio of phosphocreatine to inorganic phosphate (PCr/P(i)) following eccentric exercise. Seven healthy untrained women, 28-46 years old, performed eccentric exercise with the right m. quadriceps in an isokinetic dynamometer (Biodex, angle velocity: 60 degrees.s-1) until exhaustion, in two different experiments, with an interval of 13-23 months. In both experiments the PCr/P(i) ratio, dynamic muscle strength, CK and muscle pain were measured before the eccentric exercise (day 0) and the following 7 d. In the second experiment daily passive stretching (3 times of 30 s duration, with a pause of 30 s in between) of m. quadriceps was included in the protocol. The stretching was performed before and immediately after the eccentric exercise at day 0, and before measurements of the dependent variables daily for the following 7 d. The eccentric exercise alone led to significant decreases in PCr/P(i) ratio (P < 0.001) and muscle strength (P < 0.001), and an increase in CK concentration (P < 0.01). All subjects reported pain in the right m. quadriceps with a peak 48 h after exercise. There was no difference in the reported variables between experiments one and two. It is concluded that passive stretching did not have any significant influence on increased plasma-CK, muscle pain, muscle strength and the PCr/P(i) ratio, indicating that passive stretching after eccentric exercise cannot prevent secondary pathological alterations.

Adult↗

PubMed1997

Effects of PTH(1-34) on blood pressure, renal function, and hormones in essential hypertension: the altered pattern of reactivity may counteract raised blood pressure.

As it has been suggested that parathyroid hormone (PTH) is implicated in the pathophysiology of essential hypertension, the effects of PTH(1-34) were assessed during infusion over 120 min in ten men with essential hypertension and in ten healthy men. Ionized calcium was kept constant by a clamping technique. Mean arterial blood pressure fell slightly in the patients (116 mm Hg, median, before, and 108 mm Hg during the infusion, P < .01), but remained unchanged in the controls (median 87 mm Hg). The pulse rate rose to a similar extent in the two groups, but cardiac output, measured by the CO2 rebreathing technique, was unchanged. The glomerular filtration rate (GFR) was slightly lower in the hypertensives than in the controls at baseline (92 v 109 mL/min, P < .02), but it increased similarly during PTH infusion in both groups (+13% v +9%, medians), as did the effective renal plasma flow (+50% v +38%). The urinary rate of sodium excretion, which was similar at baseline, increased more in the patients than in the controls (+191% v +46%, P < .05); this was mainly attributable to a reduction in the tubular reabsorption of sodium. Calculations based on lithium clearance indicated that mainly the proximal tubular reabsorption of sodium decreased during PTH infusion. Baseline plasma PTH(1-84) was higher in the patients than in the controls (20.5 ng/L v 16.5 ng/L, P < .05). The baseline plasma values of renin, aldosterone, atrial natriuretic peptide, endothelin, and noradrenaline were similar in the two groups. During infusion of PTH, renin increased less in the patients than in the controls (P < .02), and aldosterone increased only in the controls (P < .01). The other hormonal values remained unchanged. In conclusion, the patients with essential hypertension had increased baseline PTH values, but nevertheless PTH had more marked vasodilative and natriuretic effects than in the controls. PTH thus seems to counteract rather than aggravate elevation of blood pressure in these patients.

Adult↗

PubMed1997

Dopamine natriuresis in salt-repleted, water-loaded humans: a dose-response study.

AIMS: The purpose of the present study was to define the dose-response relationship between exogenous dopamine and systemic haemodynamics, renal haemodynamics, and renal excretory function at infusion rates in the range 0 to 12.5 microg kg(-1) min(-1) in normal volunteers. METHODS: While undergoing water diuresis, eight subjects were infused with 0, 1, 2, 3, 5, 7.5, 10 or 12.5 microg of dopamine kg(-1) min(-1) over 2 h in a randomized and double-blind fashion. On each study day, renal clearance studies were performed during a 1 h baseline period and subsequently during the second 1 h infusion period. Lithium clearance (CL(Li)) was used to estimate proximal tubular outflow. RESULTS: Cardiac output increased with the four highest doses. Mean arterial pressure followed a biphasic pattern with a decrease during the two lowest doses and a dose-dependent increase from the 7.5 microg kg(-1) min(-1) dose onwards. Effective renal plasma flow increased with all doses of dopamine, but peaked with the 3 microg kg(-1) min(-1) infusion rate [from 617 (585-649) ml min(-1) with placebo to 915 (824-1006) ml min(-1) (means with 95% CI, P<0.001)]. None of the doses changed glomerular filtration rate (GFR). Sodium clearance (CL(Na)) and CL(Li) were elevated with the four lowest doses but increased further from 7.5 microg kg(-1) min(-1) onwards. Compared with placebo, the percentage increase in CL(Na) with increasing dose was 77 (5-159), 93 (13-172), 107 (24-190), 121 (60-181), 253 (65-441), 284 (74-494), and 212 (111-312) %, respectively. There were only small, inconsistent decreases in absolute proximal reabsorption rate (APR = GFR-CL(Li)). Fractional distal reabsorption of sodium (FDR(Na) = (CL(Li)-CL(Na))/CL(Li)) decreased with all doses, reaching its nadir with 7.5 microg kg(-1) min(-1) [from 95.9 (94.6-97.2) % with placebo to 91.5 (90.0-93.0) % (P<0.01)] whereafter a flat dose-response curve was observed. CONCLUSIONS: In conclusion, the renal vasodilating effect of dopamine was maximal with 3 microg kg(-1) min(-1). The dose-dependent attenuation seen with higher doses is consistent with an increased alpha-adrenergic stimulation opposing the effect on dopaminergic receptors. The present CL(Li) studies confirm that dopamine increases proximal tubular outflow. The results suggest that the natriuretic effect of depressor doses of dopamine was primarily caused by attenuation of the increase in distal sodium reabsorption normally seen after an increase in proximal tubular outflow. Pressor doses further increased sodium excretion, indicating the presence of pressure natriuresis at these high doses.

Adult↗

PubMed1997

Increased risk of stress fractures of the ribs in elite rowers.

In rowing, stress fractures are rare. However, the intensity of training has increased in terms of more specific rowing movements throughout the year. Simultaneously, new equipment has been developed resulting in faster rowing over the racing distance with increased risk of injuries on bones, muscles and ligaments. We report five cases of chest pain and one case of pain in the shoulder in national elite rowers, diagnosed as stress fractures of the ribs employing 99mTechnetium-MDP bone scan. In all cases, an increase or alteration in physical activity in the weeks prior to the injury and an increase in specific rowing movements with special emphasis on the new equipment, combined with increased biomechanical stress applied to the thoratic skeleton in the catch and the early part of the drive phase of the stroke, most probably caused the injuries.

Adult↗

PubMed1997

Bone scintigraphy in sports medicine: a review.

Bone scintigraphy is of growing interest to the sports physicians in the evaluation of benign disorders of the musculoskeletal system. It is atraumatic and easily applied, and being very sensitive a normal scintigram excludes pathophysiological conditions or mechanical disorders of the bones and joints. The indication is mainly suspicion of stress fractures, where a graduation is possible allowing prognostic interpretation. The finding of stress fractures in female athletes with long-lasting amenorrhea may warrant further interest in the bone mineral content of the skeleton. In the diagnostic evaluation of particularly longer-lasting joint-related pain in younger subjects without obvious degenerative disease, bone scintigraphy is very sensitive to exclude joint affection, but not very specific to reveal an exact diagnosis. In athletes with back pain and radiographically demonstrated spondylolysis, tomography of bone scintigrams (SPECT) may discern between an actively healing process, probably eliciting the pain, and an inactive, healed process not responsible for the back pain. Bone tumors always show increased uptake in bone scintigraphy, but the method does not allow a reliable differentiation between benign and malign etiology.

Adolescent↗

PubMed1997

Exercise training and the progression of chronic renal failure.

The possible beneficial effect of regular exercise training on the progression of chronic renal failure was studied in a prospective randomized controlled study. Thirty patients with a median glomerular filtration rate (GFR) of 25 ml/(min.1.73 m2) (range 10-43) were randomized to physical training (30 min of bicycling daily or an equal amount of other physical activities) or to maintenance of the usual lifestyle. The median maximal work capacity increased significantly in the exercise group and remained unchanged in the control group during a median observation time of 20 months whereas the rate of progression judged by the slope of GFR versus time plot was equal in the two groups. Hence, the beneficial effect of exercise training, earlier observed in rat studies, could not be reproduced in our patients. Physical exercise had no untoward effect on progression of renal disease.

Adult↗

PubMed1996

Plasma noradrenaline and ageing: effects of smoking habits.

We tested the hypothesis that long-term smoking is responsible for increased plasma noradrenaline (NA) in elderly healthy subjects. Thirty-nine subjects were studied both at rest and during exercise: 10 young non-smokers (median age 24 years, range 21-33), 10 young smokers (30.5 years, 27-36), 10 elderly non-smokers (64 years, 52-75) and nine elderly smokers (62 years, 56-68). The young and elderly subjects had smoked for an average of 15 years and 46.8 years respectively. Plasma NA was significantly elevated in elderly long-term smokers compared with elderly non-smokers, young non-smokers and young smokers in both supine and sitting positions (supine: 1.06 +/- 0.24 vs. 0.71 +/- 0.22, 0.53 +/- 0.12, and 0.70 +/- 0.29 nmol L-1 respectively; sitting: 3.01 +/- 0.83 vs. 2.07 +/- 0.77, 1.89 +/- 0.52 and 2.25 +/- 0.47 nmol L-1 respectively). Plasma adrenaline did not differ among the groups. At submaximal exercise (60 W), plasma NA was significantly elevated in the elderly smokers compared with the other groups, owing to the elevated basal values. Increments in plasma NA at 60, 100 and 140 W were correlated with the relative exertion and not influenced by smoking. Plasma NA increased more in young subjects than in the elderly during maximal work load (21.7 +/- 8.0 vs. 13.4 +/- 5.4 nmol L-1) and correlated with the peak O2 uptake. Total blood volume was not different among the four groups and correlated inversely with basal plasma NA. It is concluded that long-term smoking may contribute to increased basal plasma NA concentrations and probably also increased sympathetic nerve activity in elderly healthy subjects, whereas smoking has little if any effect on plasma NA responses induced by exercise. Interindividual variability in basal plasma NA concentrations may in part be explained by differences in blood volume.

Adult↗

PubMed1996

Haematological status in elite long-distance runners: influence of body composition.

In 10 female and eight male Danish elite middle- and long-distance runners, haematological status, including blood volume, was examined. Haemoglobin, haematocrit and serum (s)-ferritin concentrations were all within the normal range. In both men and women, blood volume, plasma volume and erythrocyte volume were increased in relation to various reference values. However, the runners had a low body weight due to a reduced fat level, 9.5% (7.3-15.1%) fat for the women, 5.9% (5.0-8.8%) fat (median and ranges) for the men, measured by dual-energy X-ray absorptiometry (DEXA) scanning. When the runners' body weights were 'normalized' to a reference population (25% fat for women, 15% fat for men), only plasma volume remained increased in relation to body weight for the women, whereas all the volumes remained increased for the men. This confirms that endurance training induces a true increased plasma volume. The lower erythrocyte volume in the women compared with the men could be a consequence of the generally poorer iron status in the women, indicating that a combination of haemolysis, menstruation and low caloric (iron) intake makes it difficult for trained women to obtain optimal effects on erythrocyte volume equal to those obtained by trained men. Furthermore, the study emphasizes the importance of taking body composition into consideration when comparing well-trained athletes with a reference population.

Absorptiometry, Photon↗

PubMed1996

High altitude-induced albuminuria in normal man is enhanced by infusion of low-dose dopamine.

Renal function and the urinary excretion rate of albumin (Ualb) at rest and during infusion of dopamine (3 micrograms kg-1 min-1) were investigated in eight normal volunteers at sea level and 48 h after a rapid, passive ascent to an altitude of 4350 m. Oxygen saturation decreased to 81% (77-85) (median with quartiles in parentheses) at high altitude. High altitude hypoxia increased Ualb from 3.2 micrograms min-1 (2.7-3.5) to 5.0 micrograms min-1 (3.3-6.6) (p < 0.05); increased mean arterial blood pressure from 80 mmHg (73-95) to 102 mmHg (96 108) (p < 0.01); decreased the effective renal plasma flow (ERPF) from 465 ml min-1 (412-503) to 410 ml min-1 (385-451) (p < 0.05), and increased the filtration fraction from 24% (22-27) to 28% (26-29) (p < 0.01). Glomerular filtration rate (GFR), and the renal clearances of lithium (CLi) and sodium (CNa) remained unchanged at high altitude. Dopamine increased ERPF, GFR, CLi, CNa, and decreased the filtration fraction in both environments. Infusion of dopamine further increased Ualb to 10.5 micrograms min-1 (5.5-64.8) (p < 0.05) at high altitude, but had no effect on Ualb at sea level. In conclusion, high altitude hypoxia per se increases the urinary excretion rate of albumin, which is further increased by the renal vasodilating drug dopamine. This effect of dopamine at high altitude may result from combined effects of the increase in renal plasma flow and a hypoxia-induced increase in the glomerular capillary permeability to albumin.

Adult↗

PubMed1995

Insulin resistance and hyperinsulinaemia in mild to moderate progressive chronic renal failure and its association with aerobic work capacity.

Tissue sensitivity to insulin and aerobic work capacity was measured in patients with mild to moderate progressive chronic renal failure. Twenty-nine non-diabetic patients with a glomerular filtration rate of 25 ml.min-1.1.73 m-2 (11-43) (median, range) and 15 sex, age, and body mass index matched control subjects with normal renal function were studied. Fasting blood glucose was comparable and in the non-diabetic range in the two groups as was the oral glucose tolerance test. Patients demonstrated hyperinsulinaemia both during fasting (p < 0.01) and during the test (p < 0.02). The tissue sensitivity to insulin, expressed by the amount of glucose infused during the last 60 min of a 120-min hyperinsulinaemia euglycaemic clamp (M-value) and the M/I ratio, was significantly lower in the patients than in the control subjects (M-value 404 +/- 118 vs 494 +/- 85 mg glucose/kg body weight, p < 0.02) (M/I ratio 1.77 +/- 0.71 vs 2.57 +/- 0.70 (mg/(kgBW.min) per pmol/l.100, p < 0.001). The maximal aerobic work capacity was significantly lower in the patients than in the control subjects (24 +/- 8 vs 32 +/- 11 ml O2/(kg body weight.min), p < 0.02) and positively correlated to the M-value and the M/I ratio in both groups. In conclusion, not only patients with end-stage chronic renal failure but also those with mild to moderate progressive chronic renal failure are insulin resistant and hyperinsulinaemic. The tissue sensitivity to insulin is correlated to the maximal aerobic work capacity suggesting that these patients might benefit from physical training programmes.

Adult↗

PubMed1995

Left ventricle haemodynamics and vaso-active hormones during graded supine exercise in healthy male subjects.

Left ventricle systolic and diastolic functional parameters were measured by gated equilibrium radionuclide cardiography in 12 healthy men (age 33-51 years) at rest and during graded supine exercise. The leftventricle end-diastolic volume showed an initial small (11%) increase during low submaximal exercise [from mean 163 (SD 40) at rest to mean 181 (SD 48) ml], while left ventricle end-systolic volume decreased successively [from mean 59 (SD 19) to mean 39 (SD 21) ml] with increasing exercise. Stroke volume was therefore elevated at all exercise levels compared with rest [mean 104 (SD 23) ml], and the peak value [mean 128 (SD 33) ml] was found at the lowest exercise level, contributing 40% to the initial increase in cardiac output. Cardiac output increased from mean 6.2 (SD 1.4) at rest to mean 20.2 (SD 5.0) l.min-1 at maximum. Left ventricle peak ejection and peak filling rates increased from mean 449 (SD 89) and mean 442 (SD 85) ml.s-1 at rest to mean 996 (SD 227) and mean 1255 (SD 333) ml.s-1, respectively, at maximum. The myocardium oxygen consumption, assumed to be proportional to the sum of the stroke work and the potential energy, increased fourfold, but absolute values were twice as high as expected, indicating that extrapolation from data obtained in dog hearts (as we have done) cannot be directly applied to humans. Selected vaso-active hormones were measured at all exercise intensities. Noradrenaline (NA), adrenaline (A) and angiotensin II (AII) concentrations showed a very pronounced increase at maximal exercise compared with the preceding lower intensites, while atrial natriuretic factor (ANF) and cyclic guanosinemonophosphate (cGMP) concentrations showed a more continuous increase, and dopamine (DA) remained almost unchanged. This speaks in favour of a crucial role for NA, A and AII in preserving blood pressure at maximum exercise, while DA probably has no importance for the cardiovascular homeostasis during exercise. Increases in concentrations of ANF and cGMP were highly correlated (r = 0.86). Our data supported the opinion that there is a cardiac limitation to maximal performance connected to the cardiac pumping capacity.

Adult↗

PubMed1995

Impact of immediate and delayed myocardial scintigraphy on therapeutic decisions in suspected acute myocardial infarction.

Early myocardial scintigraphic imaging has become technically feasible in patients admitted to hospital with suspected acute myocardial infarction. After prompt injection of 99mTc-sestamibi, subsequent scintigraphic imaging of perfused myocardium can be performed. During a 5-month period, 237 patients were admitted to the coronary care unit of a district hospital on suspicion of acute ischaemic syndrome, and injection of 99mTc-sestamibi for the performance of myocardial scintigraphy was carried out in 134 patients, on average 2 h after onset of symptoms. The investigation was repeated in 126 patients, on average 18 h after the injection. Three planar views were taken in the coronary care unit with a mobile gamma camera. The prevalence of acute myocardial infarction was 53%. The predictive value at the first scintigraphic imaging for a positive or negative test for myocardial infarction 54% and 56%, respectively. Even exclusion of patients with a previous infarction did not increase the diagnostic validity. The predictive value of a negative test, 77%, at the second scintigraphy was still insufficient to make immediate therapeutic decisions. Myocardial scintigraphy performed early, on suspicion of acute myocardial infarction, cannot therefore be used routinely as a diagnostic test prior to intervention in unselected patients because some 90% of this patient group have myocardial perfusion defects.

Aged↗

PubMed1995

Comparison of cardiac output measurement techniques: thermodilution, Doppler, CO2-rebreathing and the direct Fick method.

Simultaneously measured cardiac output obtained by thermodilution (TD), transcutaneous suprasternal ultrasonic Doppler (DOP), CO2-rebreathing (CR) and the direct Fick method (FI) were compared in eleven healthy subjects in a supine position (SU), a sitting position (SI), and during sitting exercise at a workload of 50 W (EX). The agreements between the techniques, two by two, were expressed as the bias calculated as the averaged differences between the techniques. Precision was expressed as the standard deviation of the bias. The overall agreement (bias +/- precision) between TD, DOP and CR respectively and FI were 2.3 +/- 1.6, -0.1 +/- 1.4, and -0.2 +/- 1.1 l/min. TD overestimated cardiac output consistently in SU, SI and EX. DOP was in-accurate during EX and agreed well with FI in SU and SI. CR agreed closely with FI in SI and EX, but values were underestimated in SU. The overall agreement between DOP and CR, respectively, and TD were 2.5 +/- 2.2 and 2.6 +/- 1.6 l/min. The overall agreement between DOP and CR was 0.1 +/- 1.6 l/min. In conclusion, TD overestimated cardiac output compared to the other techniques and the poor agreement has to be taken into consideration especially in measures of low values. The precision of DOP and CR against FI seems to be within clinically acceptable limits, and these methods may provide interchangeable alternatives to the invasive Fick method.

Adult↗

PubMed1995

Basal and exercise-induced changes in plasma catecholamines: relationship to age, smoking habits and sampling times.

Contrary to earlier investigations, we have previously shown that the initial increase in venous plasma noradrenaline (NA) during exercise did not differ in young and elderly non-smoking subjects exercising at the same relative workload (75%), and that the greatest increase at maximal workload was observed in the young subjects. In order to determine whether the observed discrepancy could be explained by long-term smoking, plasma NA and adrenaline (A) were evaluated in eight elderly male smokers (mean age 67 years). The results were compared with data reported previously [Jensen et al. (1994) Exercise-induced changes in plasma catecholames and neuropeptide Y: relation to age and sampling times. J Appl Physiol, 76, 1269-1273] in seven young (mean age 27 years) and seven elderly (mean age 61 years) non-smoking male subjects. As shown earlier, basal plasma NA was significantly increased in elderly smokers compared to young and elderly non-smokers. During exercise at 75% of maximal work capacity, no difference was observed between elderly smokers and non-smokers. No difference in plasma A was found between elderly smokers and non-smokers either at rest or during exercise. These findings indicate that the exercise-induced increase in plasma NA did not differ in elderly smokers and non-smokers despite increased resting levels in the former group, and that the increase in the elderly subjects was not augmented compared to that in young subjects.

Adult↗

PubMed1994

The transplanted human kidney does not achieve functional reinnervation.

1. Previous histological studies have demonstrated partial reinnervation of the human transplanted kidney. However, it remains unknown whether this reinnervation is of any functional significance. 2. The effects of noradrenaline infusion (2 micrograms h-1kg-1) and lower body negative pressure (-27 mmHg) on renal haemodynamics, sodium excretion and tubular function were investigated in 25 renal transplant recipients and 10 normal subjects. Sixteen of the transplant recipients had all been transplanted for more than 27 months, and nine had all been transplanted for less than 2 months. 3. After an overnight fast, the subjects were water-loaded, and clearance studies were performed with a 1 h baseline period, a 1 h period with noradrenaline infusion, another 1 h baseline period, and a final 1 h period with lower body negative pressure. 4. During noradrenaline infusion the relative decrease in effective renal plasma flow, glomerular filtration rate and clearance of lithium and sodium was significantly more pronounced in the long-term transplanted patients than in the control subjects. 5. Lower body negative pressure only depressed the glomerular filtration rate significantly in the control subjects. Further, the relative decrease in effective renal plasma flow and clearance of lithium and sodium was significantly greater in the control subjects than in the two groups of transplanted patients. 6. The present study thus demonstrated that in short- and long-term transplanted kidneys in man, supersensitivity to circulating noradrenaline and an inadequate response to lower body negative pressure was present. This strongly suggests that the human transplanted kidney remains functionally denervated.

Adolescent↗

PubMed1994

Exercise-induced changes in plasma catecholamines and neuropeptide Y: relation to age and sampling times.

Plasma norepinephrine (NE), epinephrine (E), and neuropeptide Y (NPY) were evaluated in seven young (median age 29 yr, range 21-31) and seven elderly (median age 61 yr, range 51-72) healthy subjects. They were all nonsmokers and had never smoked. Basal values and the initial increase in plasma NE and E during exercise at 75% of maximal work load were identical in the two groups. After 5 min of exercise at this load, plasma NE and E remained constant in the elderly but were still increasing in the young subjects. Plasma NE and E increased to significantly higher values after 15 min in the young subjects: 1.68 +/- 0.18 vs. 0.92 +/- 0.11 ng/ml (NE) and 0.136 +/- 0.012 vs. 0.061 +/- 0.013 ng/ml (E). Basal plasma NPY was highest at rest and increased only during exercise in the young subjects. Our results demonstrate that in nonsmokers aging is not associated with increased plasma NE levels. The blood pressure response to exercise was the same in both groups, suggesting that the increase in the sympathetic activity was adequate in the elderly. Alternatively, the higher increase in sympathetic activity in the young subjects may be attributed to their higher work capacity.

Adult↗

PubMed1994

Albuminuria and overall capillary permeability of albumin in acute altitude hypoxia.

The mechanism of proteinuria at high altitude is unclear. Renal function and urinary excretion rate of albumin (Ualb) at rest and during submaximal exercise and transcapillary escape rate of 125I-labeled albumin (TERalb) were investigated in 12 normal volunteers at sea level and after rapid and passive ascent to 4,350 m. The calcium antagonist isradipine (5 mg/day; n = 6) or placebo (n = 6) was administered to abolish hypoxia-induced rises in blood pressure. Lithium clearance and urinary excretion of beta 2-microglobulin were used to evaluate renal tubular function. High altitude increased Ualb from 2.8 to > 5.0 micrograms/min in both groups (P < 0.05). In the placebo group, high altitude significantly increased filtration fraction (P < 0.05), but this response was abolished by isradipine. Lithium clearance and urinary excretion of beta 2-microglobulin remained unchanged by hypoxia in both groups. Exercise did not reveal any further renal dysfunction. In both groups, high altitude increased TERalb from 4.8 to > 6.7%/h (P < 0.05). In conclusion, acute altitude hypoxia increases Ualb despite unchanged tubular function and independent of effects of isradipine on filtration fraction. The elevated TERalb suggests an overall increase in capillary permeability, including the glomerular endothelium, as the critical factor in high-altitude induced albuminuria.

Adult↗