Hyperhydration induced by glycerol ingestion: hormonal and renal responses

The simultaneous time courses of hydromineral hormones (renin-aldosterone system, arginine vasopressin, and atrial natriuretic peptide) and renal responses were examined during and after the completion of hyperhydration induced by glycerol and fluid ingestion. Eight healthy young male Caucasian subjects participated in two separate trials, each including three consecutive phases in a thermoneutral environment. Phases 1 and 3 involved a 90-min period at rest, while phase 2 involved a 120-min period at rest designed to provide either (i) euhydration (control trial) or (ii) hyperhydration induced by ingestion of glycerol (1.1 g/kg body mass) and fluid (21.4 mL/kg body mass). During the 2-h time period of glycerol and fluid ingestion, urine flow, urine osmolality, and plasma levels of hydromineral hormones remained at basal values. In contrast, after hyperhydration completion during phase 3, the diuresis increased markedly together with a dilution of the urine (p < 0.05) while hormonal responses did not change. These results indicate significant differences in renal responses during and after hyperhydration completion and suggest that these changes are independent of fluid-regulating hormonal responses.