Decreased uterine bradykinin receptors during captopril infusion in rats

To assess whether local tissue changes in bradykinin metabolism occur with captopril, the effect of intravenous infusion of bradykinin and captopril on bradykinin receptors in rat uterine smooth muscle was compared. Bradykinin and captopril decreased both the blood pressure and the number of bradykinin uterine receptors, estimated by direct radiolabeled binding techniques, without changing receptor affinity. These results demonstrate that bradykinin "down-regulates" its membrane receptor in rat myometrium. The similar change in receptor numbers induced by captopril could be explained by a local increase in bradykinin at receptor sites. The increase in local tissue level of bradykinin may contribute to the hypotensive action of captopril.