Circadian variations of renal functions in different states of hydration in man.
Journal/Book: Chronobiologia XII: 247 (1985). 1985;
Abstract: Institut für Arbeitsphysiologie und Rehabilitationsforschung der Universität Marburg Marburg/Lahn West Germany. The circadian rhythms of urinary volume and content of electrolytes were measured under different conditions of water supply in healthy male subjects during 3 different days. The water intake was systematically varied (100 350 and 600 ml/3h) starting 6h before the beginning of the measurements which were carried out under constant bed rest in a climatic chamber. Every 3h a standardized low-protein meal was administered. The daily courses of the urinary volume showed an increase of the mesor which was proportional to the amount of water intake and the absolute amplitude was signifcantly higher drinking 600 ml/3h. However the relative amplitude was decreased. The circadian acrophase was shifted in advance and the slope of the curves from the nightly minimum to the maximum was sinificantly increased in the experiments with 350 and 600 ml/3h fluid intake. The respetive daily courses exhibited a higher form factor. The sodium concentration showed analogue modifications whereas the rhythm of the sodium excretion did not change under the different conditions of the experiment.