EFFECT OF PHORBOL ESTER ON cAMP-DEPENDENT PROTEIN KINASE ACTIVITY IN CARDIOMYOCYTES

Cardiomyocytes isolated from neonatal rats were treated with phorbol-12-myristate-13-acetate(PMA) ranging from 10^-11 to 10^-7mol/L for 20 min,causing cytosol protein kinase A (PKA) activity to decrease while particulate PKA activity increase in a concentration-dependent manner.The change of PKA activity induced by PMA was abolished completely by pretreatment of polymyxin B or depletion of protein kinase C (PKC).Type Ⅱ PKA activity in particulate fraction was enhanced remarkably,while that of type I PKA was not altered when the cells were treated with 100 nmol/L PMA.The results suggested that subcellular distribution and activity of PKA in cardiomyocytes may be regulated by PKC.