NITRIC-OXIDE SYNTHESIS IN RAT CARDIAC MYOCYTES AND FIBROBLASTS

We investigated nitric oxide (NO) synthase activity in cultured neonat al rat cardiac myocytes and fibroblasts upon treatment with interleuki n 1 beta (IL-1 beta) and lipopolysaccharide (LPS). Incubation of cardi ac myocytes for 24 h with IL-1 beta or LPS caused a significant increa se in NO and cGMP production. Simultaneous incubation of IL-1 beta wit h N-G-monomethyl-L-arginine or transforming growth factor beta (TGF-be ta) completely inhibited the IL-1 beta-induced NO and cGMP production in cardiac myocytes. In contrast, incubation of cardiac fibroblasts fo r 24 h with IL-1 beta or LPS showed no significant effect on NO or cGM P production. Addition of IL-1 beta decreased the beating rate of card iac myocytes, but TGF-beta overcame that inhibition. These observation s suggest the presence of iNOS in cardiac myocytes, which is an import ant regulator of contractile function of the heart.