Endotoxin impairs biliary glutathione and HCO3- excretion and blocks the choleretic effect of nitric oxide in rat liver

Cholestasis in patients with sepsis has been attributed to the effects of endotoxin (lipopolysaccharides, LPS) and LPS-induced cytokines, which are also potent stimulators of systemic and hepatic nitric oxide (NO) synthesis, NO donors stimulate bile acid-independent bile flow in normal rat liver, but the effects of LPS-induced NO on bile formation remain unclear, To address this question we examined the effects of NO and its mediator guanosine 3',5'-cyclic monophosphate (cGMP) on bile now and biliary HCO3- and glutathione excretion in isolated perfused rat livers (IPRL) from LPS-treated rats, Portal and systemic NO2- + NO3- plasma levels were increased 47-fold in LPS-treated rats and were also elevated in perfusate (6-fold) and bile (9-fold) after isolating and perfusing livers from these animals. Bile flow, HCO3-, and glutathione output were decreased by 33%, 25%, and 81% in these IPRL, respectively, Stimulation of NO synthesis with L-arginine or inhibition of inducible NO synthesis with aminoguanidine did not change bile flow, although pretreatment with aminoguanidine inhibited NO production by 85%. Moreover, the choleretic effects of infusions of the NO donors sodium nitroprusside (SNP) and S-nitroso-acetyl-penicillamine were markedly reduced in endotoxemic IPRL compared with normal controls, and SNP-induced HCO3- and glutathione excretion were reduced by 61% and 86%, respectively, SNP-induced cyclic GMP production was 2.3-fold lower than in normals, but the choleretic effect of dibutyryl cGMP was only slightly reduced in endotoxemic livers, These findings indicate that LPS reduces bile acid-independent bile flow primarily by inhibiting biliary excretion of glutathione and to a lesser extent HCO3-, whereas LPS-induced NO does not modulate bile formation in endotoxemia. Thus, impairment of the major determinants of bile acid-independent bile now by LPS may contribute significantly to the pathogenesis of the cholestasis of sepsis.