Abstract
The role of coronary flow in the regulation of ventricular B-type natriuretic peptide (BNP) gene expression was studied in isolated perfused rat heart preparation. The increase of coronary flow from 5 ml/min to 20 ml/min for 2 h resulted in a 132 ± 6 mm Hg increase in aortic perfusion pressure. The changes in BNP mRNA and immunoreactive BNP (IR-BNP) levels in response to hemodynamic stress were compared to those of c-fos and adrenomedullin (ADM) gene expression. The increase of coronary flow resulted in 1.5-fold increases in the left ventricular BNP mRNA ( P < 0.001) and IR-BNP ( P < 0.05) levels in 2-month old rats. There was also a 1.5-fold ( P < 0.05) increase in ventricular c-fos mRNA levels, whereas ADM mRNA levels decreased by 74% ( P < 0.001) in the left ventricle. In 18-month old rats, the increase in coronary flow decreased left and right ventricular BNP mRNA levels by 18% ( P < 0.05) and 39 % ( P < 0.001), respectively. There were no changes in IR-BNP peptide and c-fos mRNA levels, whereas ADM mRNA levels decreased by 46% ( P < 0.001) in the left ventricles. The results show that increased aortic perfusion pressure results in differential expression of cardiac genes including up-regulation of ventricular BNP and c-fos gene expression and down-regulation of ADM gene expression. Furthermore, aging seems to elevate the threshold at which hemodynamic stress of the heart results in a response at BNP gene level.
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