Inhibition of Na Pumps Enhances Ca-dependent Release of Vasopressin from the Isolated Neurohypophysis of the Rat

Abstract

The isolated neurohypophysis of the rat was incubated with a medium lacking Ca and vasopressin release was induced by reintroduction of Ca (2mM). The response to Ca was greatly enhanced after treatment with a medium containing ouabain or lacking K. The enhanced release of vasopressin by ouabain was dependent on the concentration of external Na. The results suggest that inhibition of Na pumps leads to a rise in internal Na, thereby activating Na-dependent Ca influx mechanism associated with vasopressin release.