Upregulation of the cardiac bradykinin B2 receptors after myocardial infarction

An increase in myocardial bradykinin (BK) might be a mechanism to protect t he heart during acute myocardial infarction (MI). To characterize the regul ation of the myocardial B2 receptor during MI, we studied the expression of this BK receptor in the right ventricle (RV), left ventricle (LV) and myoc ardial septum (S) 24 h after left coronary ligation, Experiments were perfo rmed in male Wistar Kyoto rats (Iz = 10) and compared with sham operated an imals (n = 6). After total RNA extraction, the myocardial B2-receptor expre ssion was analyzed by a RNase protection assay (n = 6), using a specific pr obe from the coding region of the receptor gene. After 24 h, rats with MI w ere normotensive and showed an impaired left ventricular function. The B2-r eceptor expression of the LV of these rats was significantly elevated (2.3- fold) compared to sham operated rats. Furthermore, we found a dramatic upre gulation of the B2 receptor in the RV (7.8-fold) and a dramatic expression of B2 receptor mRNA in S of infarcted hearts, whereas in the S of sham oper ated rats no B2 receptor expression could be detected. Our data show clearl y that the described increase in BK during myocardial ischemia is accompani ed by an elevated B2-receptor expression in the infarcted and non-infarcted parts of cardiac ventricles. (C) 1999 Elsevier Science B.V. All rights res erved.