Response of cardiac myocytes to a ramp increase of diacylglycerol generated by photolysis of a novel caged diacylglycerol. Here we examine a cellular response to controlled elevation of diC8 within single cardiac myocytes. Both phases were inhibited by the protein kinase C inhibitor chelethyrine chloride. The results reveal new features in the response of cardiac muscle to diacylglycerol, including a positive inotropic phase and a complex responsiveness to a simple linear increase in diacylglycerol. Zamudio FZ, Gurrola GB, Arevalo C, Sreekumar R, Walker JW, Valdivia HH, Possani LD Department of Molecular Recognition and Structural Biology, National Autonomous University of Mexico, Cuernavaca, Morelos.
Arachidonic acid stimulates protein kinase C-epsilon redistribution in heart cells.
Here we show that arachidonic acid stimulates a unique pattern of translocation of the epsilon-isoform of protein kinase C in isolated adult rat cardiac myocytes. Using western blot analysis, the majority of epsilon-protein kinase C was found in a cytosolic fraction in unstimulated cells. The physiological relevance of these findings was supported by the observation that 50 microM arachidonic acid promoted a 2.3-fold enhancement of myocyte twitch amplitude, an effect that was significantly blocked by the protein kinase C antagonist chelerythrine. Moreover, the onset of this physiological response correlated in time with translocation of epsilon-protein kinase C to the filaments. Conversion of an inactive cardiac dihydropyridine receptor II-III loop segment into forms that activate skeletal ryanodine receptors.