Ursodeoxycholate Reduces Ethinylestradiol Glucuronidation in the Rat: Role in Prevention of Estrogen-Induced Cholestasis

Abstract

Ethinylestradiol (EE) administration (5 mg/kg, s.c., daily for 5 days) to rats leads to cholestasis, and its derivative EE 17␤-glucuronide is a likely mediator of this effect. Coadministration of ursodeoxycholate (UDC) was shown to prevent ethinylestradiol-induced cholestasis. The aim of this study was to evaluate the inhibitory effect of UDC on EE glucuronidation in vivo and in vitro as a potential mechanism to explain UDC protection. UDC treatment (25 mg/kg, i.p., daily for 5 days) decreased the biliary excretion of EE 17␤-glucuronide in bile after administration of a trace dose of [ 3 H]EE and reduced microsomal EE 17␤-glucuronidation activity by 20% and expression of UGT2B1, one of the enzymes involved in EE conjugation, by 30%. Glucuronidation kinetic studies were performed in vitro using normal microsomes and isolated hepatocytes in the presence of tauroursodeoxycholate (TUDC), the major endogenous derivative of UDC in the rat. Kinetic enzymatic studies in microsomes showed a noncompetitive inhibition of EE 17␤-glucuronidation by TUDC, which was unique for this bile salt since other endogenous bile salts such as taurocholate, taurochenodeoxycholate, or taurodeoxycholate did not affect the enzyme activity. Studies in isolated hepatocytes confirmed the inhibitory effect of TUDC on EE glucuronidation and indicated that TUDC can reach the enzyme active site in intact cells. In conclusion, both in vivo and in vitro experiments indicate that UDC decreased the metabolic pathways involved in EE glucuronidation, hence decreasing the formation of the cholestatic derivative EE 17␤-glucuronide.

Galactosamine Prevents Ethinylestradiol-Induced Cholestasis

“…As shown in Table 1, neither ALT nor AST was affected by GAL administration, indicating that the protocol used to study GAL action on biliary secretory function was not toxic. Neither of these serum markers was modified by EE, in agreement with previous results (Bouchard et al, 1993;Crocenzi et al, 2001;Sanchez Pozzi et al, 2003). However, EE treatment led to a 40% increase in ALP serum activity, a biochemical marker of cholestasis (Table 1), which was not restored by GAL coadministration.…”

Reduced hepatic extraction of palmitate in steatosis correlated to lower level of liver fatty acid binding protein

“…The steatotic rat model was established using female Wistar rats of ϳ250 g body weight. The procedure is a modification of the protocol given by Sanchez Pozzi and co-workers (30). Rats were housed and fed under standard conditions and were injected with 17␣-ethinylestradiol (2 mg/kg sc) on 8 consecutive days.…”

“…In doing so, we also collected a range of biochemical and histological parameters to examine possible correlations. Steatosis in rats was induced by administration of 17␣-ethinylestradiol (30). Also, we sought to mimic the hepatic fatty acid accumulation and symptomatological aspects of the early stages of fatty liver disease.…”

Prevention of Mrp2 Activity Impairment in Ethinylestradiol-Induced Cholestasis by Ursodeoxycholate in the Rat

“…Its beneficial effect on reversion of EE-induced cholestasis is based on the improvement of the biliary secretory function impaired by the estrogen (Jacquemin et al, 1993;Sanchez Pozzi et al, 2003). It was demonstrated that UDC up-regulates canalicular Mrp2 expression in normal mice (Fickert et al, 2001) and that its taurine derivative [tauroursodeoxycholate (TUDC)] stimulates insertion of preexisting pericanalicular vesicles containing Mrp2 into the canalicular domain, thus accounting for prevention of taurolithocholate-induced cholestasis (Beuers et al, 2001).…”

“…EE, a synthetic estrogen, induces intrahepatic cholestasis in experimental animals (Gumucio and Valdivieso, 1971;Jacquemin et al, 1993;Crocenzi et al, 2001;Sanchez Pozzi et al, 2003) by reducing the liver's capacity to excrete bile salts and organic anions (Gumucio and Valdivieso, 1971;Bossard et al, 1993). Expression of Mrp2, a canalicular transporter involved in organic anion excretion and, hence, in the formation of the bile salt-independent fraction of bile flow (Crocenzi et al, 2004), is decreased in EE cholestasis (Trauner et al, 1997).…”