Bradykinin Stimulates Endothelial Nitric Oxide (NO) Production by Calcium/Calmodulin- Dependent NO Synthase

Abstract

The cellular mechanism by which bradykinin induces nitric oxide (NO) formation was studied in cultured bovine endothelial cells. The basal release of nitrate/nitrite (NOx) from endothelial cells increased linearly during one-min incubation and reached plateau levels thereafter. Bradykinin dose-dependently and similarly stimulated NOx release and cyclic GMP production, both of which were abolished by N^G-monomethyl L-arginine. D-Arg-[Hyp³, Thio^5′8, D-Phe⁷]-bradykinin (B₂-antagonist), but not Leu⁸-des Arg⁹-bradykinin (B₁-antagonist), inhibited bradykinin-induced production of both NOx and cyclic GMP. Removal of extracellular Ca²⁺ by EGTA failed to affect bradykinin-induced NOx and cyclic GMP production, whereas intracellular Ca²⁺ release inhibitor (TMB-8) completely abolished NOx and cyclic GMP production stimulated by bradykinin. A relatively selective calmodulin inhibitor (W-7) blocked bradykinin-induced production of NOx and cyclic GMP. Our data suggest that bradykinin stimulates B₂ receptor-mediated NO formation via activation of Ca²⁺/calmodulin-dependent constitutive NO synthase, and that NO may function as an autocrine/paracrine factor in endothelial cells. (Hypertens Res 1993; 16: 131-137)