THE INFLUENCE OF POST-PITUITARY EXTRACT ON THE EXCRETION OF WATER AND CHLORIDES BY THE RENAL TUBULES

Abstract

As the NaCl content of fluid injected into post-pituitary extract treated rats is increased, the urine volume progressively increases. The inhibitory effect of the extract was overcome by the adm. of 0. 8% NaCl. At this point the conc. ceiling for chlorides was reached, and excess chlorides passing down the tubules carried with them additional amts. of water, osmotically held. The inj. of post-pituitary extract into rats given NaCl solns. ranging in conc. from 0 to 1. 2% led in all cases to increased Cl excretion, both per ccm. of urine and in total amt., compared to control animals given similar solns. The conc. of urea per ccm. of urine was inversely proportional to the urine output in both post-pituitary-injected and control series. The total amt. of urea excreted during the metabolic period was constant, indicating that the extract is without direct influence on urea output. As the dosage of post-pituitary extract was progressively reduced, the chloride-concentrating effect of the extract tended to disappear before the inhibitory effect on water excretion was affected. In partially nephrectomized animals, the salt and water changes induced by post-pituitary extract were differentiated. In these animals the extract inhibited urine flow comparably as in the controls, but concentrated the chlorides to only about 50% of the control levels. The hypothesis is now advanced that the antidiuretic hormone of the post-pituitary gland acts directly on the kidney, leading to a decreased tubular reabsorption of salt (chloride) coincident with the well-known increased tubular reabsorption of water.