Ethinyl estradiol cholestasis involves alterations in expression of liver sinusoidal transporters

Abstract

The mechanisms involved in ethinyl estradiol-induced cholestasis are controversial. Basal bile flow was reduced by ethinyl estradiol administration, with a half time (t1/2) of 12.5 +/- 0.6 h. In contrast, initial taurocholate uptake was not significantly reduced until 3 days to 59% of control and to 13 and 10% of control at 5 and 7 days, respectively. The t1/2 was 4.3 +/- 0.1 days. These physiological changes were correlated with measurement of protein mass and steady-state mRNA for Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase), Na(+)-dependent taurocholate transporter, organic anion transporters, and membrane lipid fluidity. Ethinyl estradiol significantly decreased Na(+)-K(+)-ATPase activity and membrane fluidity. However, neither Na(+)-K(+)-ATPase alpha-subunit nor beta-subunit mass was altered by ethinyl estradiol administration. In contrast, protein content of the Na(+)-dependent taurocholate transporter was significantly reduced to 21% of control (P < 0.001) at 5 days. The Na(+)-dependent taurocholate transporter was identified in sinusoidal membrane fractions as a doublet with a molecular size estimated to be 51 and 56 kDa. Although both bands were reduced with ethinyl estradiol treatment, the 56-kDa band was decreased more rapidly and to a greater extent than the 51-kDa band. The estimated t1/2 of 4.8 +/- 0.6 days for the doublet was similar to that for Na(+)-dependent taurocholate uptake. The organic anion transporter protein mass was similarly reduced with time of ethinyl estradiol administration to 21% of control (P < 0.01) at 5 days. Ethinyl estradiol also rapidly decreased the steady-state mRNA levels of Na(+)-dependent and organic anion transporters to approximately 50% and 15% of control at 5 days, respectively. These studies indicate early generalized abnormalities of the sinusoidal membrane lipid fluidity, Na(+)-K(+)-ATPase activity, and bile acid transport protein content.

Impaired activity of the bile canalicular organic anion transporter (Mrp2/cmoat) is not the main cause of ethinylestradiol-induced cholestasis in the rat

“…As shown earlier, 36 ntcp appeared as a characteristic doublet upon Western blotting, with one band at 51 kd and another, minor band at 56 kd. The latter band was affected most by EE treatment, as recently shown by Simon et al 37 Bile Formation. The effects of EE treatment for 3 days on bile flow and on bile secretion rates of bile salts, bilirubin, GSH, and total amino acids are shown in Fig.…”

Differential effects of microsomal enzyme–inducing chemicals on the hepatic expression of rat organic anion transporters, OATP1 and OATP2

“…In general, hepatic Oatp1 is down-regulated in response to toxins, chemicals, and procedures that affect bil- iary function (i.e., lipopolysaccharide, ethinyl estradiol, and bile duct ligation). [33][34][35] Although hepatic Oatp1 mRNA or protein levels are not significantly up-regulated by the chemicals evaluated in the current study, Oatp1 may be sensitive to modulation by other steroid derivatives in extrahepatic organs such as the kidney, because testosterone is known to up-regulate Oatp1 gene expression. 36 In contrast to Oatp1, the current results demonstrate that Oatp2 expression is highly responsive to chemical stimuli, because PB and PCN up-regulate, and 3-MC down-regulates, Oatp2 protein (Figs.…”

Transport of reduced glutathione in hepatic mitochondria and mitoplasts from ethanol-treated rats: Effect of membrane physical properties andS-adenosyl-L-methionine

“…In this regard, recent observations have shown that SAM feeding to ethanol-fed functioning of several membrane proteins, 45 we have exam-…”