AIM:To evaluate the effect of nitric oxide(NO)on the development and degree of liver failure in an animal model of acute hepatic failure(AHF).METHODS:An experimental rat model of galactosamine-induced AHF was used.An inhibitor of NO synthase,nitroarginine methyl ester,or an NO donor,arginine,were administered at various doses prior to or after the induction of AHF.RESULTS:All tested groups developed AHF.Following inhibition of the endogenous NO pathway,most liver parameters improved,regardless of the inhibitor dose before the induction of liver damage,and depending on the inhibitor dose after liver damage.Prophylactic administration of the inhibitor was more effective in improving liver function parameters than administration of the inhibitor after liver damage.An attempt to activate the endogenous NO pathway prior to the induction of liver damage did not change the observed liver function parameters.Stimulation of the endogenous NO pathway after liver damage,regardless of the NO donor dose used,improved most liver function parameters.CONCLUSION:The endogenous NO pathway plays an important role in the development of experimental galactosamine-induced AHF. AIM: To evaluate the effect of nitric oxide (NO) on the development and degree of liver failure in an animal model of acute hepatic failure (AHF). METHODS: An experimental rat model of galactosamine-induced AHF was used. Inhibitor NO synthase, nitroarginine methyl ester, or an NO donor, arginine, were administered at various doses prior to or after the induction of AHF.RESULTS: All tested groups developed AHF.Following inhibition of the endogenous NO pathway, most liver parameters improved, regardless of of the inhibitor dose before the induction of liver damage, and depending on the inhibitor dose after liver damage .Prophylactic administration of the inhibitor was more effective in improving liver function parameters than administration of the inhibitor after liver damage. An attempt to activate the endogenous NO pathway prior to the induction of liver damage did not change the observed liver function parameters. Optimization of the endogenous NO pathway after liver damage, regardless of the NO donor dose used, improved most liver function parameters. CONCLUSION: The endogenous NO pathway plays an important role in the development of experimental galactosamine-induced AHF.