Biphasic response to bradykinin in isolated porcine iliac arteries is mediated by bradykinin B1 and B2 receptors.

Bradykinin-induced responses were studied in isolated porcine iliac arteries. Relaxation was endothelium dependent and seen at low concentrations (10(-10)-10(-8) M) of bradykinin. It was inhibited by the bradykinin B2-receptor antagonist icatibant (HOE-140) and by the nitric oxide synthase inhibitor Nomega-nitro-L-arginine. Bradykinin-induced relaxation was significantly potentiated by the kininase I carboxypeptidase inhibitor mergepta (10(-6) M). Bradykinin (>10(-7) M) elicited contraction of preparations with or without endothelium. The contraction was abolished by indomethacin but was not affected by the thromboxane A2/prostaglandin H2-receptor antagonist SQ 29,548. Icatibant and the bradykinin B1-receptor antagonist desArg9[Leu8]bradykinin significantly decreased bradykinin-induced contraction regardless of endothelial function. The contraction also was decreased by treatment with mergepta. The bradykinin B1-receptor agonist desArg9-bradykinin contracted endothelium-denuded arterial strips. This contraction was significantly decreased by desArg9[Leu8]bradykinin but not by icatibant. The desArg9-bradykinin-induced contraction also was inhibited by the protein-synthesis inhibitor cycloheximide. Neither bradykinin-induced relaxation nor contraction was affected by the ACE inhibitors enalaprilat or cilazaprilat. In conclusion, bradykinin-induced relaxation of isolated porcine iliac arteries was mediated by endothelial bradykinin B2 receptors and mainly nitric oxide. Bradykinin-induced contraction was endothelium independent, indomethacin sensitive, and probably mediated by bradykinin B1 (inducible) and B2 receptors located in the vascular smooth-muscle layer. Kininase I carboxypeptidase, and not ACE, is the main enzyme responsible for bradykinin degradation in these vessels.