RAPID COMMUNICATIONS ATRIAL NATRlURETlC FACTOR INHIBITS VASOTOCIN-INDUCED WATER REABSORPTION IN THE TOAD URINARY BLADDER

Abstract. Peptides recent ly isolated from atr ia l ex t rac ts possess potent nat r iu re t ic and d iure t ic activit ies, which are thought to be due to hemodynamic actions, such as increased glomerular f i l t rat ion o r altered medullary blood flow. A d i rec t tubu lar site of action cannot be ru led out; therefore we have examined the effect of one of these peptides, atr iopept in Ill on vasotocin-induced water absorption in the toad uri _ b lad-w. Our resul ts indicate tha t equimolar doses ( l O w y t o 10 M) of atr iopept in I I I can signi f icant ly inh ib i t vasotocin-induced water reabsorption in v i t r o and suggest a physiologic role for the cardiac peptides to al ter water reabsorption d i rec t ly a t the level of the tubules o r collecting ducts, independent of any hemodynamic effects they might also exe r t vivo. a l g a 6 s o c i e t y f o r Exper imental Biology and Medicine. Introduct ion. At r ia l myocytes contai