Contractile Responses to Angiotensin l and Angiotensin II in Hamster Uterine Smooth Muscle 1 2

Abstract

Summary

Angiotensin I (A-I) and angiotensin II (A-II) produced dose-dependent increases in isometric tension in isolated strips of uterine smooth muscle prepared from ovariectomized golden hamsters treated with estrogen. Responses to A-II were consistent with receptor-occupancy theory of agonist-receptor interactions. Inhibition of angiotensin-converting enzyme virtually abolished responses to A-I but not those to A-II. Blockade of A-II receptors inhibited responses to both A-I and A-II. Cholinergic or α-adrenergic blockade did not alter uterine responses to either A-I or A-II. These findings suggest that contractile responses elicited in the isolated uterus of the hamster are due to its local conversion to A-II and subsequent interactions with specific A-II receptors. Such conversion occurs at least to the extent of 14 to 27%.

We are indebted to Dr. Zola P. Horovitz (Squibb Institute) for a generous supply of SQ 20881, and to Dr. Alan Castillion (Norwich Pharmacol) for a gift of l-Sar-8-Ala-angiotensin II.