Effects of oxytocin inhibitors on the natripheral and hydrosmotic responses of toad skin to oxytocin and angiotensin II

Abstract

Effects of oxytocin inhibitors on the natripheral and hydrosmotic responses of toad skin to oxytocin and angiotensin II?. Previous reports from this laboratory demonstrated that 8-Leu-angiotensin Il, an analog of angiotensin 11 (AT), significantly blocked the natriferic and hydrosmotic responses of toad skin to AT, without affecting the responses to neurohypophyseal hormones. The present work was undertaken in order to characterize the effects of oxytocin (0) analog on these responses to both 0 and AT.

4-Leu-oxytocin was found to be ineffective in inhibiting the response to 0, whereas 1-6 alpha deaminocystathionine-2-0-methyltyrosine-oxytocin (MeDCOT-1), although devoid of effects per se, proved to have a dual behavior: while inhibiting the natriferic effects of peptide hormones (0 and AT) without affecting that of catecholamines (norepinephrine), it seems to unspecifically potentiate the hydrosmotic response to all of these agents. These results dramatically contrast those previously reported by other authors for the same compound, and provide additional evidence for the existence of separate receptors for peptide hormones and catecholamines in toad skin.