Rat hypothalamic extract inhibits vasopressin‐stimulated Na+‐K+‐ATPase activity in the rat renal medulla

Abstract

Arginine vasopressin stimulates Na+-K+-ATPase activity located in the rat thick ascending limb of Henle's loop. mammalian hypothalamus appears to produce a factor capable of inhibiting Na+-K+-ATPase activity in a variety of tissues. The effect of a purified rat hypothalamic extract with and without AVP on rat renal Na+-K+-ATPase activity was evaluated by a cytochemical technique. The hypothalamic extract alone failed to affect basal Na+-K+-ATPase activity throughout renal segments after 10 min exposure. Na+-K+-ATPase activity stimulated by AVP (1-10 fmol l-1) for 10 min was inhibited by rat hypothalamic extract over the concentration range 10(-7)-10(-3) U ml-1 in a dose-dependent manner. Complete inhibition of AVP-stimulated Na+-K+-ATPase activity occurred at a hypothalamic extract concentration of 10(-3) U ml-1. Only Na+-K+-ATPase activity located in the renal medullary thick ascending limb was influenced by the rat hypothalamic extract.