INHIBITION OF TOAD BLADDER AND RAT UTERUS RESPONSES TO OXYTOCIN AND OTHER AGENTS BY TOAD BLADDER EXTRACTS

¹ Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York

Studies were undertaken to examine the inhibitory properties of toad bladder extracts. These extracts inhibit water transfer across the toad bladder wall in response to oxytocin, arginine vasotocin and theophylline, while adenosine-3',5'-phosphate is not inhibited. Rat uterus responses to oxytocin, acetylcholine and 5-hydroxytryptamine are also inhibited. The ability of the extracts to block responses to drugs of chemical natures as different as those of oxytocin and theophylline or oxytocin and acetylcholine suggests that it does not compete with these agents for their specific receptors. A comparison is made with the inhibitory activities of glutathione and cysteine. The endogenous inhibitor is destroyed by heating in strong acid or base, but not by several proteolytic enzymes.