ARACHIDONIC-ACID PRODUCTS-MEDIATED CONTRACTION INDUCED BY BRADYKININ IN RELAXED MESENTERIC ARTERIAL RINGS FROM HOLTZMAN RATS

This study describes the contractile action of bradykinin on rat isola ted mesenteric arterial rings and a possible mechanism responsible for this action. Bradykinin induced dose-dependent contraction of relaxed mesenteric arterial rings from Holtzman rats, but not from Wistar rat s. A second bradykinin challenge in the same ring induced a very small effect or no effect at all. Destruction of the endothelium did not mo dify the response to bradykinin. des-Arg(9)-[leu(8)]bradykinin failed to antagonize bradykinin's action. HOE 140 (D-Arg[Hyp(3),Thi(5),D-TiC7 ,Oic(8)]bradykinin) reduced bradykinin-induced contractions. Indometha cin abolished the contractile response to bradykinin; prostaglandin F- 2 alpha induced a long-lasting contraction, dissimilar from that induc ed by bradykinin; L-655,240 (4-chlorobenzyl)-5-fluoro-3-methyl-indol-2 -yl]-2,2 propanoic acid), an antagonist of the thromboxane receptor, i nhibited bradykinin-induced contractions. These results suggest that b radykinin-induced contraction in mesenteric arterial rings is indirect , through activation of bradykinin B-2 receptors, resulting in liberat ion of prostanoids from outside the endothelium. Thromboxane A(2) is p robably an intermediate in this response but we cannot exclude the par ticipation of other prostanoids.