Increased basal contractility of cardiomyocytes overexpressing protein kinase C epsilon and blunted positive inotropic response to endothelin-1

Objective: Protein kinase C (PKC) is thought to be involved in the regulati on of the mammalian cardiac excitation-contraction coupling process by vaso active peptides Like endothelin-1 (ET-1). However, the demonstration of a c ausal link between activation of specific PKC isoforms and the increase in contractility mediated by ET-1 is still inferential. Methods: By means of a denovirus-mediated gene transfer, we specifically overexpressed PKC epsilon in cultured adult rabbit Ventricular myocytes (Ad-PKC epsilon). Myocyte sh ortening and [Ca2+](i) transients under basal and ET-1-stimulated condition s were measured in Ad-PKC epsilon and Ad-LacZ control transfected cells. Re sults: Infection with Ad-PKC epsilon resulted in a strong, virus dose-depen dent increase in PKC epsilon protein Levels, whereas protein expression of other PKC isoforms remained unchanged. Using a multiplicity of infection of 100 plaque-forming units/myocyte, basal and cofactor-dependent PKC epsilon kinase activity was increased 28- and 90-fold, respectively, when compared to control. Myocyte basal fractional shortening and [Ca2+](i), transient a mplitude were both increased by 21% (P<0.05 each) in Ad-PKC<epsilon> transf ected myocytes when compared to Ad-LacZ transfected control myocytes. The p ositive Inotropic effect of ET-1 in control myocytes was markedly blunted i n PKC epsilon -overexpressing myocytes. Conclusion: Specific overexpression of PKC epsilon in rabbit ventricular myocytes increases basal myocyte cont ractility and [Ca2+](i) transients, and modifies their responsiveness to ET -1. (C) 2001 Elsevier Science B.V. AII rights reserved.