The effect of intense muscular work (80% of maximal oxygen uptake) on responses of plasma hormones involved in electrolyte and water balance were measured in 14 male subjects. They were divided into three groups according to their maximal oxygen uptake and the duration of exercise performed until exhaustion: well trained subjects (group I), trained subjects (group II), and untrained subjects (group III). Pulmonary gas exchange, heart rate, rectal and skin temperature, and weight loss were measured as well as hematocrit and plasma and urine sodium and potassium concentrations. Rectal temperature increased significantly in all subjects after exhaustion. The variation of hematocrit was smallest and the weight loss greatest in the well-trained subjects. Plasma aldosterone, renin activity (PRA), vasopressin (AVP), and neurophysin (Np) displayed highly significant increases after exercise in all three groups: PRA was increased 4.5 times (p < 0.01), aldosterone 13 times (p < 0.05), Np 2.6 times (p pe 0.05), and AVP 4.8 times (p < 0.05). Nevertheless, there was no correlation between the changes in PRA and those in plasma aldosterone, nor between aldosterone and plasma sodium or potassium. At the urinary level, the only striking observation was that free water clearance tends to become positive after exercise. Our results provide evidence that this kind of exercise produces a highly significant increase in plasma levels of the hormones involved in electrolyte and water balance. They also indicate that it is among the well-trained subjects that sweat loss is highest though the hematocrit increase is the smallest; this suggests that water is shifted more efficiently from the extravascular compartment.

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PubMed1979

[Radioimmunoassay of ADH in human urine (author's transl)].

A simple efficient procedure for extracting and concentrating arginine-8-vasopressin (AVP) from urine has been coupled with a specific and sensitive radioimmunoassay in order to measure antidiuretic hormone (ADH) excretion in normal humans under various physiological stimuli. Antisera have been raised in rabbits injected with lysine-vasopressin (LVP) or AVP coupled with bovine serum albumin. The antiserum selected for the assay which inhibits the antidiuresis induced in the rat by AVP is used at a final dilution of 1 : 50,000 and possesses a high association constant of 1 x 10(11) 1.mol-1. The limit of detection of the RIA system is 0.5 micronUI/ml of urine (1.25 pg). Urinary ADH has been extracted from urine by Miller and Moses method. Mean recovery of added vasopressin averaged 90.2% +/- 11 (SD) and assay of serial dilutions of such extracts showed that they behave in the assay system in the same way as synthetic AVP standards. Moreover comparison of the results obtained by the RIA to those given by the biological method using the ethanol anesthetized rat showed excellent correlation (r = 0.9 p less than 0.001). Under ad libitum fluid and food intake, mean daily urinary excretion of AVP (uncorrected for recovery) determined in 22 subjects was found to be 30.58 +/- 11.64 mU/h with no significant difference between men and women. In response to an oral waterload ADH became undetectable at the peak of diuresis. Following a 16 hr fluid deprivation, ADH rose moderately. A significant correlation has been found between urine osmolality and AVP excretion rate.

Adult↗

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