Regulation of the isozymes of protein kinase C in the surviving rat myocardium after myocardial infarction: distinct modulation for PKC-alpha and for PKC-delta

Objective The goal of this study was to clarify the regulation of the isozymes of protein kinase C (PKC) in the process of remodeling after myocardial infarction. Methods An in vivo model of regional myocardial infarction induced by ligation of the left anterior coronary artery in rats was used. Hemodynamic parameters and the heart and lung weights were determined 1 week and 1, 2 and 3 months after operation. In transmural biopsies from the non-ischemic left ventricular wall of the infarcted heart, PKC activity (ELISA) and the expression of its major isozymes, PKC-α, PKC-δ and PKC-ε (Westernblot analysis) were determined. Results As early as one week after myocardial infarction, heart weight and left ventricular enddiastolic pressures were significantly increased. Lung weights increased after 2 – 3 months, indicating progressive pulmonary congestion. The activity of PKC was significantly increased about 1.8-fold after 1 week, decreasing progressively in the later time course. Whereas the expression of PKC-ε did not change, PKC-α was increased after 1 month (157 %) and then returned to baseline values. In contrast, PKC-δ expression was significantly augmented after 2 and 3 months of myocardial infarction (187 %). Conclusions These data demonstrate for the first time that in the remodeling heart after myocardial infarction, a subtype-selective regulation of the PKC isozymes occurs: The upregulation of PKC-α coincides with the development of hypertrophy, whereas the extensive upregulation of PKC-δ outlasts the process of developing hypertrophy and persists in the failing heart. The trigger mechanisms for this newly characterized process remains to be elucidated. Received: 25 October 2001, Returned for revision: 3 December 2001, Revision received: 19 December 2001, Accepted: 20 December 2001