In cultured rat cardiac myocytes, LPS-induced nitric oxide synthase activation decreased peak systolic intracellular Ca2+ (790 to 551 nM, P<0.05) and cell contraction amplitude (100 to 72.4%, P<0.05).
p-value: p=<0.05
Recent work has demonstrated that endotoxin or cytokines induce nitric oxide synthase in heart or cardiac myocytes. We investigated the functional significance of inducible nitric oxide synthase (iNOS) in indo 1-loaded beating myocytes with regard to intracellular Ca2+ concentration (Ca2+i) and cell contraction. Lipopolysaccharide (LPS; 10 micrograms/ml) time dependently induced iNOS mRNA and protein in cultured neonatal rat cardiac myocytes. Nitrite concentration in the medium and intracellular guanosine 3',5'-cyclic monophosphate (cGMP) contents after 24-h exposure to LPS increased in proportion to the levels of iNOS induction in these cells. Myocytes treated with both NG-monomethyl-L-arginine and LPS for 24 h expressed iNOS protein, but nitrite production was significantly inhibited. Subsequent perfusion with 100-fold molar excess L-arginine of these myocytes elicited decreases in peak systolic Ca2+i (790 +/- 42 to 551 +/- 27 nM, P < 0.05), relative amplitude of cell contraction (100 to 72.4 +/- 5.5%, P < 0.05), and spontaneous beating rate (146 +/- 13 to 85 +/- 22 beats/min, P < 0.05). Pretreatment with methylene blue or KT-5823 inhibited these negative myocardial effects. These results suggest that LPS induces iNOS in cardiac myocytes and that the increased nitric oxide produced by iNOS has cardiac depressant effects through the activation of cGMP-dependent protein kinase.
Kinugawa et al. (Wed,) conducted a other in Cultured neonatal rat cardiac myocytes. Lipopolysaccharide (LPS) and L-arginine was evaluated on Peak systolic intracellular Ca2+ concentration, relative amplitude of cell contraction, and spontaneous beating rate (p=<0.05). In cultured rat cardiac myocytes, LPS-induced nitric oxide synthase activation decreased peak systolic intracellular Ca2+ (790 to 551 nM, P<0.05) and cell contraction amplitude (100 to 72.4%, P<0.05).