Abstract: The effect of endogenous and exogenous nitric oxide(NO) on protein kinase(PKC) activity in cultured neonatal rat cardiomyocytes was examined.The results were as following:Activity of PKC was decreased by NO precursor L-arginine(L-Arg) (10^-5～10^-2 mol/L,30 min) and NO donor sodium nitroprusside (SNP)(10^-6～10^-3 mol/L,5 min)in a dose-dependent manner in cultured neonatal rat cardiomyocytes.Activity of PKC increased by a PKC activator phorbol 12-myristate 13-acetate(PMA)(10-5mol/L,15 min) was impaired by a NO precursor L-Arg and a exogenous NO donor SNP.NG-nitro-L-argingie methyl ester(L-NAME),a nitric oxide synthase (NOS) blocker,itself had no effect on the PKC activity of cultured neonatal rat cardiomyocytes,but may inhibite the role of PKC activity induced PMA.These results indicate that PKC was decreased by endogenous and exogenous NO in a dose-dependent manner.The role of NO on rat cardiomyocytes intracellular signaling transduction pathway may be controlled through PKC.PKC may turn into key site or important signaling element of this effect.

Key words: neonatal rat myocardial cell culture, nitric oxide, protein kinase C, phorbol 12-myristate 13-acetate