RESUMO
In experiments on puppies ageing from 3 days up to 8 months, as well as on adult dogs, studies have been made of mechanisms of excretion of water and sodium during the increase of osmotic concentration in the blood circulation of the liver and spleen. It was found that in contrast to adult dogs, in which the osmotic shift decreases diuresis and increases sodium excretion, the decrease of diuresis in 1-month puppies is accompanied by a decrease of sodium excretion. Two-component osmoregulatory reaction is developed only to the 2nd month of life. Pituitrin P, injected intravenously, evoked the same reactions which were observed in osmoregulatory reflexes at various stages of ontogenesis. Studies on papillary-cortical osmotic and sodium gradients implies that kidney reactions to osmotic shifts are realized via neurohypophysial hormones; maturation of mechanisms realizing the osmotic papillary-cortical gradient takes place previously to those which realize sodium concentration gradient.
