ABSTRACT
We examined the effect of endogenous and exogenous nitric oxide (NO) on protein kinase C (PKC) activity induced by angiotensin II (Ang II) in cultured neonatal rat cardiomyocytes. The results are as follows. The activity of PKC was increased by Ang II (0.01-10 micromol/L) in a dose-dependent manner, but decreased by NO precursor L-arginine (L-Arg) (10 micromol/L-10 mmol/L) in a dose-dependent manner in cultured neonatal rat cardiomyocytes. Pretreatment with L-Arg (100 micromol/L) decreased significantly Ang II -activated PKC activity and PKC activity induced by phorbol 12-myristate 13-acetate (PMA) ( 10 micromol/L), a PKC activator. Pretreatment with N(G)-nitro-L-argingie methyl ester (L-NAME), a nitric oxide synthase (NOS) blocker, may inhibit significantly the role of L-Arg on Ang II - and PMA-activated PKC activity. The activity of PKC was also decreased by NO donor sodium nitroprusside (SNP) (10 micromol/L-1 mmol/L) in a dose-dependent manner in cultured neonatal rat cardiomyocytes. Pretreatment with SNP (10 micromol/L) decreased significantly Ang II - and PMA-activated PKC activity. These results indicate that PKC was controlled by both NO and Ang II. PKC may be a cross talk between Ang II and NO in cardiomyocytes. NO abolished the activity of PKC and impaired PKC downstream signaling transduction pathway cascades.