Captopril Increases the Affinity of Bradykinin Receptor Binding Sites in Bovine Coronary Arterial Endothelial Cells

Abstract

In a radioligand binding study using bovine coronary artery endothelial cell membranes, captopril changed a single bradykinin(BK)binding site(K_d=1.77 nM, B_max=60.2 fmol/mg protein)to high−(K_d=0.68 pM, B_max=17.7 fmol/mg protein)and low−(K_d1.00 nM, B_max=72.5 fmol/mg protein)affinity binding sites.This effect was reversed by GppNHp.Captopril also enhanced BK−induced endothelium−dependent relaxation in saponin−treated coronary rings, and GppNHp partially suppressed this enhancement.These results suggest that captopril may affect BK receptors that couple to G−proteins.