Norepinephrine-induced changes in cardiac transforming growth factor-β isoform expression pattern of female and male rats

Transforming growth factor-beta (TGF-beta) is a ubiquitous growth-regulating protein with an essential role in tissue repair and formation of extracellular matrix (ECM). To better understand the role of different isoforms of TGF-beta in the cardiac remodeling process induced by norepinephrine (NE), the expression of TGF-beta1, TGF-beta2, and TGF-beta3 was studied and compared with the expression of collagen. NE (0.1 mg/kg.h) was intravenously infused in female and male Sprague-Dawley rats for several time periods, and freshly obtained ventricular myocardium after 1 day was dissociated into myocyte and nonmyocyte fractions. Prazosin (0.1 mg/kg.h) and metoprolol (1 mg/kg.h) were used to block alpha- and beta-adrenoceptors, respectively. After NE infusion, the three isoforms of TGF-beta were differentially induced as far as the magnitude and the time course is concerned. The increased expression of TGF-beta2 started earlier with a maximum after 12 hours and was more pronounced (10-fold elevation) than that of the other two isoforms, with a clear specificity for the left ventricle in female hearts. This specificity was also seen in male rats with 16-fold elevation of TGF-beta2 after 1 day of NE-stimulation. The increase of TGF-beta2 was significant only in the myocyte fraction obtained from female as well as from male hearts. The expression of the mRNA of all TGF-beta isoforms of collagen type I and type III, and of the matrix metalloproteinase (MMP)-2 and its inhibitor TIMP-2 was reduced predominantly by alpha-adrenoceptor blockade with prazosin. The increase in TGF-beta isoforms correlated with that of the mRNA expression of collagens, MMP-2 and TIMP-2.