Decreased protein kinase C-epsilon expression in hypertrophied cardiac ventricles induced by triiodothyronine treatment in the rat

To examine the effect of thyroid hormone-induced cardiac hypertrophy on PKC expression, changes in the expression of PKC isoforms were studied in hype rtrophied cardiac ventricles induced by triiodothyronine (T3) injection in the rat. Injection with T3 for 8 days induced 49% increase in cardiac weigh t compared to controls. Immunoblot analysis of cardiac ventricular extracts showed the expression of PKC-delta, -epsilon, and -zeta in both control an d T3-treated groups. The expression of PKC-epsilon decreased by 40% in hype rthyroid rat cardiac ventricles, while PKC-delta and -zeta expressions were barely affected. PKC-epsilon immunoreactivity decreased in both cytosol an d membrane fractions. On the contrary, PKC-epsilon expression did not decre ase in the extract of hypertrophied cardiac ventricles produced by aortic b anding or aortocaval shunt. These results indicate that thyroid hormone dow n regulates PKC-E expression in the hyperthyroid-mediated cardiac hypertrop hy. (C) 2000 Elsevier Science Inc. All rights reserved.