Increased formation of S-nitrothiols and nitrotyrosine in cirrhotic rats during endotoxemia

Plasma S-nitrosothiols are believed to function as a circulating form of ni tric oxide that affects both vascular function and platelet aggregation. Ho wever, the formation of circulating S-nitrosothiols in relation to acute an d chronic disease is largely unknown. Plasma S-nitrosothiols were measured by chemiluminescence in rats with biliary cirrhosis or controls, and the ef fect of lipopolysaccharide (LPS) on their formation was determined. Plasma S-nitrosothiols were increased in rats with cirrhosis (206 +/- 59 nM) compa red to controls (51 +/- 6 nM, p < .001). Two hours following injection of L PS (0.5 mg/kg) plasma S-nitrosothiols increased to 108 +/- 23 nM in control s (p < .01) and to 1335 +/- 423 nM in cirrhotic rats (p < .001). The plasma clearance and half-life of S-nitrosoalbumin, the predominant circulating S -nitrosothiol, were similar in control and cirrhotic rats, confirming that the increased plasma concentrations were due to increased synthesis. Becaus e reactive nitrogen species, such as peroxynitrite, may cause the formation of S-nitrosothiols in vivo, we determined the levels of nitrotyrosine by g as chromatography/mass spectrometry as an index for these nitrating and nit rosating radicals. Hepatic nitrotyrosine levels were increased at 7.0 +/- 1 .2 ng/mg in cirrhotic: rats compared to controls (2.0 +/- 0.2 ng/mg, p < .0 1). Hepatic nitrotyrosine levels increased by 2.3-fold and 1.5-fold in cont rol and cirrhotic rats, respectively, at 2 h following injection of LPS (p < .01). Strong positive staining for nitrotyrosine, was shown by immunohist ochemistry in all the livers of the rats with cirrhosis. We conclude that t here is increased formation of S-nitrosothiols and nitrotyrosine in biliary cirrhosis, and this is markedly upregulated during endotoxemia. (C) 2001 E lsevier Science Inc.