Effects of conjugated linoleic acid isomers in the phospholipase C gamma1 response to oxidative stress in isolated cardiomycytes

The present study was conducted to examine the role of a major cardiac phospholipase C (PLC) isozyme, PLC gamma1, in cardiomyocytes during oxidative stress and thereafter to examine the role of CLA isomers on the PLC gamma1, response to oxidative stress. Left ventricular cardiomyocytes were isolated by collagenase digestion from adult male Sprague-Dawley rats (250-300 g) and treated with 20, 50 and 100 muM H2O 2 for 15 minutes. A concentration-dependent increase in the mRNA level and membrane protein content of PLC gamma1 was observed with H2O2 treatment. Furthermore, PLC gamma1, was activated in response to H2O2, as revealed by an increase in the phosphorylation of its tyrosine residues. However, catalase prevented the H2O2 induced activation of PLC gamma 1. There was also a marked increase in the phosphorylation of the anti-apoptotic protein, Bcl-2 by H2O2; a PLC inhibitor, U73122, attenuated this change. Furthermore, while both PKC delta and &egr; protein contents were increased in the cardiomyocyte membrane fraction in response to H2O2 only PKC &egr; activation was almost completely prevented by the PLC inhibitor, U73122 (2 muM). (Abstract shortened by UMI.)...