Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes

G. Taimor, K.-D. Schlüter, K. Frischkopf, M. Flesch, S. Rosenkranz and H. M. Piper. Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes. Journal of Molecular and Cellular Cardiology (1999)31 , 2127–2136. As shown before, TGF β acts in an autocrine manner on the induction of hypertrophic responsiveness to β -adrenoceptor stimulation in cultured ventricular cardiomyocytes of adult rat. We now investigated how TGF β expression and activation is regulated in these cultures and how β -adrenoceptor stimulation influences TGF β -mRNA expression. It was found that freshly isolated cardiomyocytes secrete latent TGF β in the culture medium. Supplementation of the cultures with 20% FCS resulted in activation of the secreted TGFβ to 4.1±0.2 ng/ml active TGF β after 6 days. Presence of the protease inhibitor aprotinin (50μ g/ml) reduced TGF β activity by 44±5% (n=5, P