Nitrite and Nitrate Levels in Patients with Cirrhosis of the Liver: Influence of Kidney Function and Fasting State

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Abstract
Increased serum nitrite/nitrate (NOx) levels, the stable metabolites of nitric oxide (NO), have been reported in patients with cirrhosis. NOx levels, however, are influenced not only by endogenous NO synthesis but also by urinary NOx excretion and dietary intake. We attempted to elucidate factors that influence NOx levels independently of endogenous NO production and to determine the conditions under which NOx levels reflect endogenous production in patients with cirrhosis and healthy controls. NOx serum concentrations and urinary NOx excretion were determined by means of the Griess reaction in relation to Child-Pugh score, kidney function, fasting state, and after exposure to tap water. Multifactor regression analysis showed inulin clearance (P = 0.0074) and Child-Pugh score (P = 0.0001) to be independent factors predicting NOx levels in patients with cirrhosis. NOx serum levels correlated negatively with the inulin clearance (P < 0.0001), which deteriorated with progressive loss of liver function. NOx levels decreased by about 30% within a 24-h fasting period. After 24 h fasting urinary NOx excretion was not significantly increased in patients with advanced cirrhosis. NOx serum levels, taken as a surrogate for endogenous NO formation, have to be viewed with caution in patients with cirrhosis because they often have impaired kidney function. However, in steady-state conditions after an adequate fasting period NOx levels might be good prognostic markers in patients with cirrhosis since they reflect two possible sequelae of liver insufficiency-namely, increased NO formation and impaired kidney function.