Bradykinin Receptors in Intestinal Smooth Muscles and Their Postreceptor Events Related to Calcium

Abstract

THE effects of trifluoperazine and verapamil on bradykinin- and des-Arg9-bradykinin induced responses of isolated rat duodenum and guinea-pig ileum were investigated to elucidate post-bradykinin receptor events. Verapamil and trifluoperazine inhibited bradykinin induced relaxations and contractions and des-Arg9-bradykinin induced contractions in rat duodenum. Bradykinin induced contractions of ileum were also inhibited by trifluoperazine and verapamil. Since non-competitive affinity constants of trifluoperazine and verapamil for the relaxant responses to bradykinin in duodenum and for the contractile responses to bradykinin in ileum are different, post-bradykinin receptor events related to calcium may be different in ileum and duodenum. In addition, affinity constants of bradykinin in guinea-pig ileum and rat duodenum are also disparate suggesting the presence of different types of bradykinin B2 receptors in these two organs.