[Age features of kidney response on food and physical loads in athletes--skiers]

The features of renal functions in older adolescents and young adults involved in ski racing, before and after water, food, and physical activity has been studied. Renal functions in the morning as baseline demonstrated an increase in GFR and greater maturity of osmoregulatory mechanisms (higher excretion of osmotically active substances, osmotic concentration index, the reabsorption of solute-free fluid) in adult compared with adolescents. After food intake in youths osmoregulatory mechanisms provided adequate renal response--increased excretion of ions in exchange for urea, that saved osmolality. In adolescence, there was an increase of excretion of osmotically active substances in parallel with the output of urine, higher GFR and reabsorption of solute-free liquid, that confirmed the lower maturity of osmoregulatory system. The renal homeostatic response after physical training indicated involvement of volume regulatory mechanisms that did not differ between age groups. It is concluded that the development of the definitive volume regulation became earlier than osmoregulation.