Background & Aims: The components of the kinin system, including kinongens, kininogenases, and B2 and B1 receptors, are expressed and activated during inflammation. Here, we investigated the expression of the kinin B2 receptor messenger RNA, kininogen and kallikrein immunoreactivity, and the ability of kinins to contract control and inflamed gallbladders in vitro. Methods: Human gallbladders, obtained from patients undergoing cholecystectomy either for acute cholecystitis secondary to gallstone disease or during elective gastro-enteropancreatic surgery (controls), were processed for reverse-transcription polymerase chain reaction analysis, kallikrein and kininogen immunohistochemistry, binding studies, and in vitro contractility studies. Results: Tissue expression of B2 receptor messenger RNA and specific binding of [3H]-bradykinin increased significantly in acute cholecystitis compared to controls. Kallikrein immunoreactivity was detected in the epithelium and infiltrating leukocytes, whereas kininogen immunoreactivity in the lumen of blood vessels and interstitial space. Bradykinin contracted isolated strips of control and acute cholecystitis gallbladders. In acute cholecystitis tissue, efficacy of bradykinin was higher than that of control gallbladders and similar to that of cholecystokinin. The contraction induced by bradykinin was significantly attenuated by B2 receptor antagonism but not by cyclooxygenase inhibition and B1, muscarinic, or tachykinin receptor antagonism. Conclusions: All the components of the kinin system are expressed in the human gallbladder. Bradykinin is a powerful spasmogen via B2 receptor activation in the normal and, especially, in the inflamed human gallbladder
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