Submitted on December 2, 2002
Accepted on April 11, 2003
ESTRADIOL-17
-D-GLUCURONIDE INDUCES ENDOCYTIC INTERNALIZATION OF BSEP IN THE RAT
Fernando A. Crocenzi1, Aldo D. Mottino1, Jingsong Cao2, Luis M. Veggi1, Enrique J. Sanchez Pozzi1, Mary Vore2, Roger Coleman3, and Marcelo G. Roma1*
1 Instituto de Fisiologia Experimental, Universidad Nacional de Rosario, Rosario, Santa Fe, Argentina
2 Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky, USA
3 School of Biosciences, The University of Birmingham, Birmingham, United Kingdom
* To whom correspondence should be addressed. E-mail: ifise1{at}citynet.net.ar.
Endocytic internalization of the multidrug-resistance-associated protein 2, Mrp2, was previously suggested to be involved in estradiol-17
-D-glucuronide (E217G)-induced cholestasis. Here, we evaluated in the rat whether a similar phenomenon occurs with the bile salt export pump, Bsep, and the ability of dibutyryl-cAMP (DBcAMP) to prevent it. E217G (15 µmol/kg, i.v.) impaired bile salt (BS) output and induced Bsep internalization, as assessed by confocal microscopy and western blotting. Neither cholestasis nor Bsep internalization occurred in TR- rats lacking Mrp2. DBcAMP (20 µmol/kg, i.v.) partially prevented the decrease in bile flow and BS output, and substantially prevented E217G-induced Bsep internalization. In hepatocyte couplets, E217G (50 µM) diminished canalicular accumulation of a fluorescent BS and decreased Bsep-associated fluorescence in the canalicular membrane; DBcAMP (10 µM) fully prevented both effects. In conclusion, our results suggest that changes in Bsep localization are involved in E217G-induced impairment of bile flow and BS transport, and that DBcAMP prevents this effect by stimulating insertion of canalicular-transporter-containing vesicles. Mrp2 is required for E217G to induce its harmful effect.
