Increased 19 kDa protein phosphorylation and protein kinase C activity in pressure-overload cardiac hypertrophy.

The aim of the study was to determine the role of protein kinase C (PKC) in protein phosphorylation in hypertrophied C. myocytes, particularly the phosphorylation of the 19 kDa protein which corresponds to myosin light chains. In myocardial hypertrophy the PKC activity in the cytosolic fraction of tissue homogenate was increased up to 253% of control hearts, and in membrane fraction up to 140% of the control value. Phorbol ester (TPA), the specific activator of protein kinase C, stimulated phosphorylation of the 19 kDa protein obtained from isolated myocytes to 181 +/- 9% of control value in normal and to 248 +/- 66% in hypertrophic myocytes. Taken together, these data suggest that protein kinase C might be involved in the increased phosphorylation of cardiac myosin light chain protein in myocardial hypertrophy.