Plasma renin activity,aldosterone and catecholamine levels when swimming and running

Summary The purpose of this study was to determine the response of plasma renin activity (PRA), plasma aldosterone concentration (PAC) and catecholamines to two graded exercises differing by posture. Seven male subjects (19–25 years) performed successively a running rest on a treadmill and a swimming test in a 50-m swimming pool. Each exercise was increased in severity in 5-min steps with intervals of 1 min. Oxygen consumption, heart rate and blood lactate, measured every 5 min, showed a similar progression in energy expenditure until exhaustion, but there was a shorter time to exhaustion in the last step of the running test. PRA, PAC and catecholamines were increased after both types of exercise. The PRA increase was higher after the running test (20.9 ng AngI · ml^–1 · h^–1) than after swimming (8.66 ng AngI · ml^–1 · h^–1). The PAC increase was slightly greater after running (123 pg · ml^–1) than swimming (102 pg · ml^–1), buth the difference was not significant. Plasma catecholamine was higher after the swimming test. These results suggest that the volume shift induced by the supine position and water pressure during swimming decreased the PRA response. The association after swimming compared to running of a decreased PRA and an enhanced catecholamine response rule out a strict dependence of renin release under the effect of plasma catecholamines and is evidence of the major role of neural pathways for renin secretion during physical exercise.     

Baroreflex sympathetic activation increases threshold pressure for the pressure-dependent renin release in conscious dogs

Stimulus-response curves relating renal-venous-arterial plasma renin activity difference (P.R.A.-difference) to mean renal artery pressure (R.A.P.) were studied in seven chronically instrumented conscious foxhounds with a daily sodium intake of 6.1 mmol/kg. R.A.P. was reduced in steps and maintained constant for 5 min using an inflatable renal artery cuff and a pressure control system.The stimulus-response curve obtained during control conditions (C) or during common carotid artery occlusion (C.C.O.) could be approximated by two linear sections: a rather flat section or plateau-level of P.R.A.-difference at normal blood pressure or above, and a very steep section between a distinct threshold pressure and 65–70 mm Hg. While the parameters of the curves varied from dog to dog, the curves kept their inique shape in the individual dog for at least 1 week. C.C.O. had no effect on the plateau-level of the P.R.A.-difference (C:0.98±0.14,C.C.O.:0.99±0.14 ng Al·ml^–1·h^–1) and on the slope of the curve below threshold pressure (C:–0.379±0.041,C.C.O: –0.416±0.082 ng Al·ml^–1·h^–1·mm Hg^–1) but shifted the stimulus-response curve to the right and increased threshold pressure (C:92.7±2.8,C.C.O.:109.7±4.1 mm Hg;P<0.05).Renal blood flow, which was measured simultaneously in three of the dogs, showed good autoregulation down to 70 mm Hg under resting conditions and was not affected by C.C.O. except for a 30% reduction of renal blood flow at the lowest pressure step (70 mm Hg).-Adrenergic blockade in 4 of the dogs reduced the plateau-level of the P.R.A.-difference from 0.86±0.19 to 0.36±0.05 ng AI·ml^–1·h^–1 (P<0.05) but had no effect on the increase of threshold pressure elicited by C.C.O.It is concluded that the stimulus-response curve for the pressure-dependent renin release has a remarkable long-term stability in the individual dog. The curve is shifted to the right by a moderate carotid baroreflex increase of renal sympathetic nerve discharge which leaves total renal blood flow largely unchanged. It is suggested that the increase in threshold pressure is independent of -adrenergic effects.This study was supported by the German Research Foundation within the SFB 90, HeidelbergA priliminary part of this investigation has been presented to the meeting of the German Physiological Society, Dortmund, March 1984 [Pflügers Arch (1984) suppl 400:R11,41]     

The influence of long-term infusion of the calcium antagonist diltiazem on postischemic acute renal failure in conscious dogs

Summary The influence of long-term infusion of the calcium-entry blocker diltiazem on postischemic acute renal failure was investigated in conscious dogs monitored by implanted instruments. In 18 uninephrectomized beagle dogs on a salt-rich diet, an electromagnetic flow probe and an inflatable plastic cuff were placed around the renal artery. Acute renal failure was induced by inflating the cuff for 180 min in the conscious animal. Group A (n=5, control) received an intraaortic injection of 0.9% NaCl (5 ml/day) from the 3rd day before until the 7th day after ischemia and group B (n=6, posttreatment) an intra-aortic injection of diltizem (5 µg·min^–1·kg^–1) beginning at the end of ischemia until the 7th day. Group C (n=7, pre- and posttreatment) received diltiazem from the 3rd day before until the 7th day after ischemia. In group A, renal blood flow dropped from 149±16 (preischemic) to 129±29 ml·min^–1 on the 1st day after ischemia. In contrast, renal blood flow increased on the 1st postischemic day in both treatment groups by 29±15% (group B,P 0.05) and 14±13% (group C). In the following days, there was no significant difference in renal blood flow between groups A, B and C. In group B, the reduction of the glomerular filtration rate was similar to that in the control group. In group C, the glomerular filtration rate was significantly less reduced than in group A (34±1.8 preischemically to 17±5.4 on day 1,P 0.05 and 20±4.1 ml·min^–1 on day 7,P 0.05). Plasma renin activity increased in both diltiazem groups, more pronounced so in group B (from 3.7±1.0 on day 1 to 16.2±7.9 ng ATI·ml^–1·h^–1 on day 7,P 0.05). In contrast to groups A and B, the increase in fractional sodium excretion was less pronounced in group C. Likewise, the decrease in free water-reabsorption was less marked than in groups A or B. It was apparent that diltiazem, when administered pre- and post-ischemically, preserved glomerular filtration rate and renal blood flow. When diltizem was given solely postischemically there was an improvement in renal blood flow, but no significant influence on glomerular filtration rate. We therefore conclude that mainly tubular factors, in addition to the attenuation of postischemic vasoconstriction, are involved in the protective effect of diltiazem on postischemic acute renal failure in conscious dogs.Abbreviations ARF acute renal failure - C_osmol clearance of osmolarity - E_Na urinary excretion rate of sodium - FE_Na fractional excretion rate of sodium - GFR glomerular filtration rate - HR heart rate - NE norepinephrine - PAM mean arterial blood pressure - PRA plasma renin activity - RBF renal blood flow - RVR renal vascular resistance - T_H2_O free water reabsorption - V_U urine volume     

Role of the macula densa in the control of renal renin gene expression in two-kidney/one-clip rats

This study was designed to examine whether macula densa function is involved in the changes of renal renin gene expression upon acute hypoperfusion of one kidney. To block macula densa function, rats with free access to salt and water were subcutaneously infused with furosemide (12 mg/day) for 6 days. Then, 4 days after the start of the infusion, the left renal arteries were clipped with 0.2-mm silver clips and renin mRNA levels in ipsilateral and contralateral kidneys, as well as plasma renin activities (PRA), were determined 48 h after clipping. In non-clipped animals furosemide increased PRA from 10 to 47 ng angiotensin I · h^–1 · ml^–1 and raised renin mRNA levels in both kidneys 2.5-fold. In vehicle-infused animals, clipping of the left renal artery increased PRA to 37 ng angiotensin I · h^–1 · ml^–1 and led to a 5-fold rise of renin mRNA levels in the ipsilateral kidneys and to a suppression to 20% of the control values in the contralateral kidneys. PRA values in clipped and furosemide-infused animals were 45 ng angiotensin I · h^–1 · ml^–1. In these animals renin mRNA levels increased in the ipsilateral kidneys to similar absolute values as in vehicle-infused rats, whilst contralateral renin mRNA levels fell to about 25% of the respective controls. These findings indicate that the stimulations of renin gene expression by inhibition of macula densa salt transport and by renal artery clipping are not additive, suggesting that the macula densa mechanism may participate in the stimulation of renin gene expression upon hypoperfusion. The macula densa mechanism, however, appears to be not essentially involved in the suppression of renin gene expression in the contralaterals to stenosed kidneys.     

Renal hemodynamics and proteinuria in running and swimming beagle dogs

Summary In beagle dogs swimming, in contrast to treadmill running, was found to cause an increase in urine flow and urinary protein excretion. Renal blood flow measured by electromagnetic flow probes decreased by 13.0±4.9% when the treadmill gradient was 15% and arterial pressure was elevated by 11.6±4.9%. Immersion resulted in an immediate decrease in renal blood flow of 8.8±5.1% and a 24.6±6.9% increase in arterial pressure. Acid-base status indicated a respiratory alkalosis in all running experiments, no net change in five swimming experiments in which hyperventilation occured, but a metabolic acidosis in eight swimming experiments without hyperventilation. During running there was a threefold increase in oxygen consumption. We conclude that swimming possibly induces more sympathetic nervous activity than treadmill running in dogs, while an alkalosis is consistently present during running, but acid-base response is variable during swimming.     

Endothelium derived relaxing factor is involved in the pressure control of renin gene expression in the kidney

To study the influence of endothelium derived relaxing factor/nitric oxide (EDNO) on renin gene expression, the effects of a 2-day treatment with the NO-synthase inhibitor nitro-L-arginine-methylester (L-NAME, 40 mg/kg twice a day) on plasma renin activity (PRA) and renal and adrenal renin m-RNA levels were examined in conscious rats with and without unilateral renal clips (0.2 mm). In sham-clipped animalsL-NAME led to a decrease of PRA from 7.5 to 2.5 ng angiotensin I (ANGI) · h^–1 · ml^–1 and to a 35% decrease of renal renin m-RNA levels. Unilateral renal artery clipping increased PRA to 35 and to 13 ng ANGI · h^–1 · ml^–1 in vehicle and inL-NAME-treated rats, respectively. In the clipped kidneys renin m-RNA levels increased to 450% of control values in vehicle-treated animals and to 220% of control values inL-NAME-treated animals. In the contralaterals as opposed to clipped kidneys, renin m-RNA levels decreased to 16% and 50% of the control values in vehicle- and inL-NAME-treated animals, respectively. In the adrenal glands renin m-RNA levels were not significantly changed either by clipping of one renal artery or by treatment of animals withL-NAME. The NO-donor sodium nitroprusside (100 M) was found to increase renin secretion and renin m-RNA levels in primary cultures of renal juxtaglomerular cells. These findings suggest that EDNO is involved in the control of the renin gene by the renal perfusion pressure.     

The role of the cardiac nerves in the regulation of sodium excretion in conscious dogs

Conscious, chronically instrumented dogs, maintained on a high sodium intake, were used to investigate whether surgical cardiac denervation impairs the natriuresis associated with left atrial pressure increase produced in three ways: during an increase in left atrial pressure by means of a reversible mitral stenosis (protocol 1); after an i.v. saline load (1.0 ml 0.9%·saline min^–1·kg^–1 over 60 min) (protocol 2); after an oral saline load (14.5 mmol Na·kg^–1 given with the food as an isotonic solution) (protocol 3).During a reversible mitral stenosis, in intact dogs, urine volume and sodium excretion increased markedly (from 34–145 l·min^–1·kg^–1 and from 3–12 mol·min^–1·kg^–1); mean arterial pressure increased by an average of 2 kPa (15 mm Hg) and heart rate by 55 b/min; plasma renin activity fell from 0.37–0.21 ng Al·ml^–1·h^–1. Cardiac denervation eliminated these effects of left atrial distension except for a small increase in heart rate (12 b/min). This indicates that the natriuresis and diuresis during left atrial distension resulted from stimulation of receptors located in the left atrium.In contrast, during protocol 2 and 3, the same amounts of sodium and water were excreted in the cardiac denervated dogs as compared to the intact dogs. A comparable decrease in plasma renin activity also was observed. — Apparently the presence of the cardiac nerves is not a prerequisite for maintenance of sodium and water homeostasis.     

Effect of dehydration and rapid rehydration on renal function and on plasma renin and aldosterone levels in the black Bedouin goat

Bedouin goats in the extreme deserts of the Middle East are regularly subjected to severe dehydration and possess a capacity to rapidly rehydrate by drinking large volumes of water. Urine flow, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in the fully hydrated animals amounted to 0.74±0.4 ml · min^–1, 76±29 ml · min^–1 and 344±146 ml · min^–1 respectively. In goats that were dehydrated to a loss of about 30% of their initial body weight, urine flow dropped to 24% of the value recorded in the hydrated animals and GFR and ERPF dropped to half their level recorded in the hydrated phase. Na and K⁺ excretion decreased in the water depleted goats and further decrease was recorded following drinking. Following drinking the urine flow, GFR and ERPF of the recently rehydrated goats dropped to below the rates recorded in the dehydrated animals. During the 3 h of the continuous recording that followed the drinking, all three rates did not exceed the predrinking level. Plasma renin activity amounted to 0.37±0.32 ng AI·ml^–1·h^–1 in the hydrated animals. In dehydrated ones it amounted to 4.8±2.8 ng AI·ml^–1·h^–1 and a further increase was recorded following drinking. Aldosterone in the hydrated goats was 5.5±4.3 ng% and increased to 13.9±2.3 ng% in the dehydrated animal and amounted to 20.1±5.5 ng% 2 h following drinking. It is concluded that the kidney in the Bedouin goat plays a major role in conserving both water and solutes, not only when deprived of water but also following its rapid rehydration.     

Tubuloglomerular feedback and autoregulation of glomerular filtration rate in Wistar-Kyoto spontaneously hypertensive rats

Experiments were done in Wistar-Kyoto spontaneously hypertensive rats (SHR) to examine the efficiency of autoregulatory adjustments of kidney and nephron filtration rate (GFR) to acute changes in blood pressure (BP) over a broad blood pressure range. When BP of the SHR was reduced from 158±7 to 118 ±3 mm Hg by aortic clamping, kidney-GFR remained unchanged from 1.19±0.11 to 1.17±013 ml·min^–1·g^–1 kidney weight (KW), respectively. Single nephron GFR (SNGFR) measured at early distal tubule sites was similarly unchanged with the same BP change, 27.9±1.5 vs. 24.9±2.1 nl·min^–1·g^–1 KW (P>0.10). Proximal and distal estimates of SNGFR were significantly different from each other at high BP (7 nl·min^–1·g^–1,P<0.025), but were not different at low BP (2.0 nl·ml^–1·g^–1,P>0.10). Studies assessing tubuloglomerular feedback activity were done with orthograde perfusion of the loop of Henle using recollections of early proximal flow rate (EPFR) as an index of change of glomerular filtration rate. A change in perfusion rate from 0 to 45 nl·min^–1 induced a reduction in early proximal flow rate of 40.5 ±4.5%. Juxtaglomerular renin activity of superficial nephrons was 36.2±4.3 in the SHR, a value insignificantly different from 23.7±4.4 ng Angiotensin II amide·0.1 ml^–1·h^–1. 5 glomeruli^–1 in normal controls (P>0.05). The SHR appears to behave as a normal animal with respect to tubologlomerular feedback and autoregulatory renal vascular adjustments. Like normal rat models, the SHR demonstrated dependence on maintenance of distal filtrate delivery to achieve single nephron GFR autoregulation.Financial support for these studies and for Dr. Ploth were made available by funds from the Deutsche Forschungsgemeinschaft     

Physical conditioning in rats influences the central and peripheral catecholamine responses to sustained exercise

We have investigated the effect of treadmill running in rats (25m · min^–1 using a 3 % gradient; for 1 h or 2 h) on the cortical extracellular concentrations of noradrenaline (NA) and its main metabolites — 3,4-dihydroxyphenylglycol and 3-methoxy-4-hydroxyphenylglycol-and the plasma adrenaline (A) and NA concentrations in relation to prior physical conditioning (1 or 2-h running -day-¹ for 12 days). Cortical microdialysates and peripheral blood were collected during 1-h resting, 1-h or 2-h running and for 1 h after exercise. Catecholamines and their metabolites were quantitated using high performance liquid chromatography with electrochemical detection. Treadmill running stimulated concomitantly peripheral catecholamine secretion and central noradrenergic activity, i.e. NA turnover and release. The effect extended into the recovery period even more as the duration of the run increased. Prior physical conditioning greatly influenced the central and peripheral catecholamine responses: the 1-h trained rats experienced the 2-h run as a stressful new event eliciting great long-lasting catecholamine responses, whereas the 2-h trained rats exhibited a progressive sustained catecholamine increase with an earlier onset of the central NA release. The data are discussed in relation to the psychological and intellectual effects of exercise and physical fitness in humans. In addition, the positive correlation found between the central noradrenergic activation and peripheral A secretion confirmed and extended our previous observations in exercising men and gave support to the hypothesis that the elevation of circulating A can be a relevant factor mediating — directly or indirectly — the exercise-induced central effects.     

Finger and forearm vasodilatatory changes after local cold acclimation

Summary To determine the vascular changes induced by local cold acclimation, post-ischaemia and exercise vasodilatation were studied in the finger and the forearm of five subjects cold-acclimated locally and five non-acclimated subjects. Peak blood flow was measured by venous occlusion plethysmography after 5 min of arterial occlusion (PBF_isc), after 5 min of sustained handgrip at 10% maximal voluntary contraction (PBF_exe), and after 5 min of both treatments simultaneously (PBF_isc+exe). Each test was performed at room temperature (25° C, SE 1 C) (non-cooled condition) and after 5 min of 5'C cold water immersion (cooled condition). After the cold acclimation period, the decrease in skin temperature was more limited in the cold-acclimated compared to the non-acclimated (P<0.01). The PBF_isc was significantly reduced in the cooled condition only in the cold-acclimated subjects (finger: 8.4 ml · 100 ml^–1 · min^–1, SE 1.1,P<0.01; forearm: 5.8 ml · 100 ml^–1 · min^–1, SE 1.5,P<0.01) compared to the non-cooled condition. Forearm PBF_exe was significantly decreased in the cooled condition only in the cold-acclimated subjects (non-cooled: 7.4 ml · 100 ml^–1 · min^–1, SE 1.2; cooled: 3.9 ml · 100 ml^–1 ·min^–1, SE 2.6,P<0.05) indicating that muscle blood flow was also reduced. The application of PBF_isc+exe elicited an increase in peak blood flow only in the forearm of the non-acclimated subjects (non-cooled: 10.4 ml· 100 ml^–1 · min^–1, SE 2.0; cooled: 14.3 ml · 100 ml^–1 · min^–1, SE 2.6,P<0.05) and conversely only in the finger of the cold-acclimated (non-cooled finger: 25.7 ml · 100 ml^–1 · min^–1, SE 4.4; cooled finger: 19.2 ml · 100 ml^–1 · min^–1, SE 3.3,P<0.01). Therefore, subjects cold-acclimated locally showed decreased vasodilatatory responses only when exposed to cold.     

Training-overtraining: influence of a defined increase in training volume vs training intensity on performance,catecholamines and some metabolic parameters in experienced middle- and long-distance runners

Summary The influence of an increase in training volume (ITV; February 1989) vs intensity (ITI; February 1990) on performance, catecholamines, energy metabolism and serum lipids was examined in two studies on eight, and nine experienced middle- or long-distance runners; seven participated in both studies. During ITV, mean training volume was doubled from 85.9 km · week^–1 (pretrial phase) to 174.6 km within 3 weeks. Some 96%–98% of the training was performed at 67 (SD 8)% of maximal performance. During ITI, speed-endurance, high-speed and interval runs increased within 3 weeks from 9 km · week^–1 (pretrial phase) to 22.7 km · week^–1 and the total training distance from 61.6 to 84.7 km · week^–1. The ITV resulted in stagnation of running velocity at 4 mmol lactate concentration and a decrease in total running distance in the increment test. Heart rate, energy metabolic parameters, nocturnal urinary catecholamine excretion, low density, very low density lipoprotein-cholesterol and triglyceride concentrations decreased significantly; the exercise-related catecholamine plasma concentrations increased at an identical exercise intensity. The ITI produced an improvement in running velocity at 4 mmol lactate concentration and in total running distance in the increment test; heart rate, energy metabolic parameters, nocturnal catecholamine excretion, and serum lipids remained nearly constant, and the exercise-related plasma catecholamine concentrations decreased at an identical exercise intensity. The ITV-related changes in metabolism and catecholamines may have indicated an exhaustion syndrome in the majority of the athletes examined but this hypothesis has to be proven by future experimental studies.     

The role of posture on the changes in plasma atrial natriuretic factor and arginine vasopressin levels during immersion

Summary In seven healthy male volunteers we investigated changes in plasma atrial natriuretic factor ([ANF]), arginine vasopressin ([AVP]) and plasma volume (PV) during supine immersion. Twenty minutes head-out water immersion in a supine position in a thermo-neutral water bath attenuated the increase in PV induced by 20 min in a supine position in air, but increased the mean plasma [ANF] from 32.0 pg · ml^–1, SEM 5.1 to 53.3 pg · m^–1, SEM 3.6 and decreased the mean plasma [AVP] from 1.4 pg · ml ^–1, SEM 0.1 to 0.9 pg · ml^–1, SEM 0.04. Simultaneously, diuresis and natriuresis increased markedly. During a 20-min control period in the supine posture without immersion, PV, plasma [ANF] and [AVP] remained unaffected while diuresis and natriuresis did not increase to the same extent. These data suggest that an increase in the central blood volume induced by a weak external hydrostatic pressure during supine immersion triggered the changes in plasma [ANF] and [AVP] and that the increase was probably due to a shift of blood volume from peripheral to central vessels. The changes in plasma [ANF] contributed to the changes in natriuresis.     

Immediate physiological responses of healthy volunteers to different types of music: cardiovascular,hormonal and mental changes

A group of 20 healthy volunteers [10 women, 10 men; median age 25 (20–33) years] were examined by means of pulsed wave Doppler echocardiography, blood sample analysis and psychological testing before and after listening to three different examples of music: a waltz by J. Strauss, a modern classic by H. W. Henze, and meditative music by R. Shankar. To assess small haemodynamic changes, mitral flow, which reflects left ventricular diastolic behaviour, was measured by Doppler ultrasound. Heart rate, arterial blood pressure and plasma concentrations of adrenocorticotropic hormone, cortisol, prolactin, adrenaline, noradrenaline, atrial natriuretic peptide (ANP) and tissue plasminogen activator (t-PA) were determined simultaneously. Transmitral flow profile is characterized by early E-wave and late atrial induced A-wave. Velocity-time integrals were measured and the atrial filling fraction was calculated. The mental state was measured by using a psychological score (Zerssen) with low values (minimum 0) for enthusiastic and high values (maximum 56) for depressive patterns. Music by J. Strauss resulted in an increase of atrial filling fraction (AFF; 29% vs 26%;P<0.05) and ANP (63 pg·ml^–1 vs 60 pg·ml^–1;P<0.05). The mental state was improved (Zerssen: 6.5 vs 11 points;P<0.05). After the music of H. W. Henze prolactin values were lowered (7.7 ng·ml^–1 vs 9.1 ng·ml^–1;P<0.01). The music of R. Shankar led to a decrease of cortisol concentrations (57 ng·ml^–1 vs 65 ng·ml^–1;P<0.001), noradrenaline concentrations (209 g·l^–1 vs 256 g·l^–1;P<0.01) andt-PAantigen concentrations (1.1 ng·ml^–1 vs 1.4 ng·ml^–1;P<0.05). Heart rate and blood pressure remained unchanged during the whole experiment. We concluded that different types of music induced changes of left ventricular diastolic function and plasma hormone concentrations. After rhythmic music (Strauss) AFF and ANP increased significantly, the mental state being improved. Meditative music (Shankar) lowered plasma cortisol, noradrenaline and t-PA concentrations; the observed increase of early left ventricular filling was not statistically significant. Prolactin concentrations decreased after modern music (Henze). Thus, it would seem to be possible to detect cardiovascular changes following different types of music by Doppler ultrasound and hormone analysis, meditative music having promising therapeutic implications in the treatment of conditions of stress.This paper contains data from J. Vollert's work for his doctoral degree.     

Effects of exercise training on plasma catecholamines and blood pressure in labile hypertensive subjects

Summary Plasma catecholamine concentrations (norepinephrine, NE; epinephrine, E) were measured along with heart rate (HR) and blood pressure (BP) at rest in supine (20 min) and standing (10 min) positions and in response to cycle ergometer exercise (5 min; 60% estimated maximal aerobic power) in 12 hypertensive patients before and after 20 weeks of aerobic training on cycle ergometer (six males, one female) or by jogging (five males). In a control group of labile hypertensive patients (five males, two females), estimated maximal aerobic power as well as HR and BP at rest in the supine and standing positions and in response to exercise were not modified from the first to the second evaluation (43±4 vs 43±5 ml·kg^–1·min^–1). In comparison estimated maximal aerobic power significantly increased in both training groups (cycle: 38±4 to 43±4; jogging: 38±3 to 46±4 ml·kg^–1·min^–1). However HR and BP were not modified following training, except for small reductions in systolic (18.9 to 18 kPa: 142 to 135 mmHg) and diastolic pressures (13.3 to 12 kPa: 100 to 90 mmHg) (p<0.05) at standing rest in the cycle group. Changes in plasma E and NE concentrations at rest and in response to exercise were small and not consistent: plasma NE was lower at standing rest following cycle training, (559±95 vs 462±108 pg·ml^–1) but a similar reduction was observed in the control group (428±45 vs 321±28 pg·ml^–1); plasma E was lower at rest following cycle training (29±7 vs 12±8 pg·ml^–1), but was higher in response to exercise (137±24 vs 419±113 pg·ml^–1). These results are in accordance with previous reports which do not clearly demonstrate that physical training in hypertensive patients lowers BP and the activity or reactivity of the sympathetic system.     

Control of mineralocorticoid substitution in Addison's disease by plasma renin measurement

Summary In 7 out-patients with Addison's disease, plasma renin activity (PRA), plasma concentrations of angiotensin II (AT II), renin substrate (PRS), potassium, sodium and total protein, hematocrit, blood pressure, heart rate and body weight were studied after 2 weeks each on 2 mg of dexamethasone, 25 mg hydrocortisone (HC), 25 mg HC+0.05 mg 9--fluorohydrocortisone (FC), 25 mg HC+0.1 mg FC and 25 mg HC+0.2 mg FC. Four further patients were less extensively studied. Mean PRA (upper normal limit, ambulatory: 12 ng AT I·ml^–1·h^–1) after the 5 steps of incremental substitution, starting with dexamethasone, was 192, 59, 38, 24 and 9 ng AT I·ml^–1·h^–1 rsp. PRS did not change with increasing substitution. PRA and AT II were significantly correlated (r=0.91;p<0.0001) and proved to be the most sensitive parameters of insufficient mineralocorticoid substitution. With decreasing significance, PRA also correlated with plasma protein concentration, plasma sodium concentration (negative), body weight (negative), heart rate, mean blood pressure (negative) and plasma potassium concentration.PRA or AT II measurements are useful clinical tools to control mineralocorticoid substitution in Addisonian patients. Inappropriately high substitution can be prevented by keeping PRA in the upper normal range.Presented in part to the 21st Symposium of the Deutsche Gesellschaft für Endokrinologie, Munich, February 1975     

The monitoring of the menstrual status of female athletes by salivary steroid determination and ultrasonography

Summary This study was designed to evaluate whether traditional plasma hormone determinations can be adequately replaced by measurements of salivary hormones. Eleven young sportswomen with menstrual irregularities attributed to strenuous physical exercise participated in this study. Mean body weight expressed as a percentage of ideal body weight was 92%, SD 4%. Their mean weekly training distance was 35 km, SD 15. Basal plasma endocrinological measurements revealed a hypo-oestrogenic status (mean plasma oestradiol values: 22pg-ml^–1, SD 8.8), and a deficient luteal phase (mean plasma progesterone: 2.9 ng · ml^–1, SD 2.1). Preexercise salivary sex steroids were low. Salivary progesterone levels were 39.3 pg · ml^–1, SD 9.5 (normal ranges in saliva: 25–60 pg· ml^–1), salivary oestrone (E₁) was 12.2 pg · ml^–1, SD 2.3 (normal ranges in saliva: 7.5–25 pg·ml^–1), and salivary oestradiol (E₂) < 1.9 pg · ml^–1, SD 1.1 (normally 1.0–10.0 pg · ml^–1). After a 21-km run, all salivary steroids appeared to increase. Mean salivary testosterone levels increased by 15.2% and salivary progesterone by 14.8%. Mean salivary oestrogens also increased (E₁: + 13.9%; E₂: +21.1%). These findings confirm the results of earlier studies which found higher post-exercise plasma sex steroid levels. Since salivary measurements are believed to reflect non-protein-bound, thus free steroid levels, the results obtained by these techniques may provide a more realistic picture of the hormonal effects of physical exercise. In future, more accurate, cost-effective and easier techniques for salivary measurements may offer additional advantages.     

Vascular fluid shifts and endocrine responses to exercise in the heat

Summary This study examines the relationships between vascular changes and endocrine responses to prolonged exercise in the heat, associated with dehydration and rehydration by fluids of different osmolarity. Five subjects were exposed, in a 34 C environment for 4 h of intermittent exercise on a cycle ergometer at 85±12 Watts (SD). Fluid regulatory hormones and cortisol were analysed in 3 experimental sessions: one without any fluid supplement (NO FLUID), and two with progressive rehydration, either by spring water (WATER) or isotonic solution (ISO), given after 70 min of exercise. Results were expressed in terms of differences between the mean values observed at the end of the exercise and the first hour values taken as references.Dehydration (NO FLUID) elicited a 4.0±0.8% (SE) decrease in plasma volume (PV) and an increase in osmolarity (8.4±3.1 mosmol · l^–1). Concomitantly, plasma aldosterone (PA), renin activity (PRA), arginin vasopressin (AVP) and cortisol (PC) levels increased greatly in response to exercise in the heat (PA: 37.2+-10.8 ng. 100 ml^–1; PRA: 13.4±2.5 ng · ml^–1 · h^–1; AVP: 3.8±1.3 pg · ml^–1; PC: 12.2±2.7 g · 100 ml^–1). Rehydration with water led to decreased osmolarity (–8.2±2.1 mosmol · l^–1) with no significant changes in PV. With ISO, PV increased by 6.0±1.3% and the decrease in osmolarity was –5.8±1.8 mosmol · l^–1. With both modes of rehydration, the increases in PRA, AVP and cortisol were blunted; only ISO prevented the rise in PA.These data indicate that prolonged exercise in moderate heat is extremely effective in increasing cortisol and fluid-electrolyte regulatory hormones in dehydrated subjects. Progressive rehydration with water or isotonic solution, in the absence of osmotic and volemic stimuli, prevents the hormonal increases.     

Autoregulation of renal blood flow,glomerular filtration rate and renin release in conscious dogs

The relationship between renal artery pressure (RAP), renal blood flow (RBF), glomerular filtration rate (GFR) and the renal venous-arterial plasma renin activity difference (PRAD) was studied in 22 chronically instrumented, conscious foxhounds with a daily sodium intake of 6.6 mmol/kg. RAP was reduced in steps and maintained constant for 5 min using an inflatable renal artery cuff and a pressure control system.Between 160 and 81 mm Hg we observed a concomitant autoregulation of GFR and RBF with a high precision. The break off points for GRF- and RBF-autoregulation were sharp and were significantly different from each other (GFR: 80.5±3.5 mm Hg; RBF: 65.6±1.3 mm Hg;P<0.01). In the subautoregulatory range GFR and RBF decreased in a linerar fashion and ceased at 40 and 19 mm Hg, respectively.Between 160 mm Hg and 95 mm Hg (threshold pressure for renin release) PRAD remained unchanged; below threshold pressure PRAD increased steeply (average slope: 0.34 ng AI·ml^–1·h^–1· mm Hg^–1) indicating that resting renin release may be doubled by a fall of RAP by only 3 mm Hg. At the break-off point of RBF-autoregulation (66 mm Hg) renin release was 10-fold higher than the resting level.It is concluded that under physiological conditions (normal sodium diet) GFR and RBF are perfectly autoregulated over a wide pressure range. Renin release remains suppressed until RAP falls below a well defined threshold pressure slightly below the animal's resting systemic pressure. RBF is maintained at significantly lower pressures than GFR, indicating that autoregulation of RBF also involves postglomerular vessels. Our data are in agreement with the myogenic hypothesis as a basic mechanism of autoregulation.This study was supported by the German Research Foundation (FG Niere, Kr. 546/5-1, Projekt 3). A preliminary report of a part of this investigation has been presented to the Vth European Colloquium on Renal Physiology 1985 (Kirchheim et al., Renal Physiol, Basel 9:84, abstract 80, 1986)     

The effect of training on responses of Β-endorphin and other pituitary hormones to insulin-induced hypoglycemia

Summary We studied whether the previously reported intensified -endorphin response to exercise after training might result from a training-induced general increase in anterior pituitary secretory capacity. Identical hypoglycemia was induced by insulin infusion in 7 untrained (Skeletal muscle enzyme activity, fiber composition and in relation to distance running performance 49±4 ml · (kg · min)^–1, mean and SE) and 8 physically trained (Skeletal muscle enzyme activity, fiber composition and in relation to distance running performance 65±4 ml · (kg · min)^–1) subjects. In response to hypoglycemia, levels of -endorphin and prolactin immunoreactivity in serum increased similarly in trained (from 41±2 pg · ml^–1 and 6±1 pg · ml^–1 before hypoglycemia to 103±11 pg · ml^–1 and 43±9 pg · ml^–1 during recovery, P<0.05) and untrained (from 35±7 pg · ml^–1 and 7±2 pg · ml^–1 to 113±18 pg · ml^–1 and 31±8 pg · ml^–1 P<0.05) subjects. Growth hormone (GH) was higher 90 min after glucose nadir in trained (61±13 mU · l^–1) than in untrained (25±6 mU · l^–1) subjects (P<0.05). Levels of thyrotropin (TSH) changed in neither of the groups. It is concluded that, in contrast to what has been formerly proposed, training does not result in a general increase in secretory capacity of the anterior pituitary gland. TSH responds to hypoglycemia neither in trained nor in untrained subjects. Finally, differences in -endorphin responses to exercise between trained and untrained subjects cannot be ascribed to differences in responsiveness to hypoglycemia.