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_d= 1.00 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.