RESUMO
The circadian rhythm of urine formation was studied in younger (27 +/- 8 yr) and aged (76 +/- 3 yr) males. In 11 younger healthy examined persons a decrease of diuresis during the night as compared with the day time was due to a rise of solute free water reabsorption. In 31 aged males the change of the urine formation rhythm with increase of the nocturnal diuresis is based on a rise of osmolal clearance combined with an increase of the solute free water reabsorption. It is shown that blockade of autacoid secretion leads to normalization of the diuresis circadian rhythm. In 10 aged men, nocturia was due to a decrease of vasopressin secretion which resulted in a decrease of the solute free water reabsorption and an increase of diuresis. The obtained data are considered as an evidence for the role of renal autacoids, alongside with vasopressin, in regulation of the circadian rhythm of the kidney function.
