Bradykinin B1 and B2 receptors differentially regulate cardiac Na+-H+ exchanger, Na+-Ca2+ exchanger and Na+-HCO3- symporter.

Bradykinin B(1) and B(2) receptors are up-regulated in the infarcted myocardium, and both receptors are involved in the regulation of intracellular pH and Ca(2+). The present study investigated the role of bradykinin B(1) and B(2) receptors in the regulation of Na(+)-H(+) exchanger (NHE-1), Na(+)-Ca(2+) exchanger (NCE-1) and Na(+)-HCO(3)(-) symporter (NBC-1) in the infarcted myocardium. NHE-1, NCE-1 and NBC-1 mRNA expression was determined by Northern blot analysis and the protein levels by Western blot analysis. Measurements were performed 1, 7 and 14 days after induction of myocardial infarction. Localization of NHE-1, NCE-1 and NBC-1 within the myocardium was studied using confocal microscopy. Cardiac morphology was measured in picrosiris-red-stained hearts. Rats were treated with placebo, the bradykinin B(2) receptor antagonist icatibant (0.5 mg/kg/day) or the bradykinin B(1) receptor antagonist des-Arg(9)-[Leu(8)]bradykinin (1 mg/kg/day). Treatment was started 1 week prior to surgery and continued until 1, 7 and 14 days post infarction. NHE-1, NCE-1 and NBC-1 mRNA expression and protein levels were increased 1 day and reached maximum values on day 7 post infarction. NHE-1 was localized in the plasma membrane, NCE-1 in the membrane of the sarcoplasmatic reticulum and NBC-1 near the Z-line. Icatibant reduced NHE-1 and inhibited NCE-1 mRNA- and protein up-regulation, while des-Arg(9)-[Leu(8)]bradykinin had no effect on NHE-1 and NCE-1 expression and translation. Transcriptional and translational up-regulation of NBC-1 was unaffected by the bradykinin B(1) and B(2) receptor antagonists. Icatibant, but not des-Arg(9)-[Leu(8)]bradykinin, limited infarct size and reduced left ventricular dilation, septal thickening and interstitial fibrosis post infarction. Bradykinin B(2) receptors are involved in transcriptional and translational regulation of NHE-1 and NCE-1 in the ischemic myocardium. Chronic B(2) receptor blockade might exert an anti-ischemic effect via limitation of NHE-1-mediated acidosis and NCE-1-mediated Ca(2+)-overload.