Renal function in human pregnancy. V. Effects of oxytocin on renal hemodynamics and water and electrolyte excretion.

Abstract

Abstract It is generally believed that oxytocin exerts a minimal antidiuretic effect when compared to Pitressin or that it may, in certain animal species, exert a diuretic action. In this study, the effects of oxytocin on renal hemodynamics and water and electrolyte excretion were studied in pregnant and nonpregnant women, in healthy men, and in patients with diabetes insipidus. One natural and two synthetic oxytocic preparations were employed. In each instance, the intravenous infusion of oxytocin induced a marked fall in urine flow which lasted for the duration of the infusion. Renal plasma flow, glomerular filtration rate, electrolyte excretion, and osmolal clearance did not change significantly, whereas free water clearance fell, and often became negative. In the pregnant subjects who received oxytocin for labor induction, the antidiuretic action became evident before the oxytocic effect. Rapid intravenous injections of single doses of oxytocin did not have any action on the urine flow. To investigate the possibility that oxytocin antidiuresis might be mediated through stimulation of antidiuretic hormone secretion, oxytocin was infused, into two patients with diabetes insipidus and three normal subjects whose endogenous antidiuretic hormone release had been blocked by alcohol. The same fall in urine flow and in the free water clearance occurred, suggesting that oxytocin has a direct action on the kidney. It is concluded that in man oxytocin has antidiuretic properties closely similar to those of Pitressin.