Prolactin increases atp-dependent taurocholate transport in
canalicular plasma membrane from rat liver.
Liu, Yong, Frederick J. Suchy, Jeffrey A. Silverman, and Mary Vore.
DEPARTMENT OF PHARMACOLOGY, GRADUATE CENTER FOR TOXICOLOGY,
UNIVERSITY OF KENTUCKY, LEXINGTON, KY (YL, MV); PEDIATRIC
GASTROENTEROLOGY/HEPATOLOGY SECTION, DEPARTMENT OF PEDIATRICS, YALE
UNIVERSITY SCHOOL OF MEDICINE, NEW HAVEN, CONNETICUT (FJS);
LABORATORY OF EXPERIMENTAL CARCINOGENESIS, NATIONAL CANCER INSTITUTE,
NATIONAL INSTITUTE OF HEALTH, BETHESDA, MARYLAND (JAS)
APStracts 3:0163G, 1996.
The taurocholate (TC) secretory rate maximum (SRm) in the isolated
perfused liver is increased in postpartum rats and ovariectomized
rats (OVX) treated with ovine prolactin (oPRL). The present studies
were designed to characterize the mechanism(s) by which oPRL
increases TC transport in the liver. oPRL (300 [mu]g/day, iv, 7 days)
increased the SRm 1.6-fold from 185 to 364 nmol/min/mg protein in the
perfused rat liver and the Vmax for ATP-dependent transport 1.7-fold
from 66 to 109 nmol/min/mg protein in canalicular plasma membrane
(cLPM) vesicles without changing Km (5-6 [mu]M). The oPRL-mediated
increases in biliary excretion in the perfused liver and ATP
-dependent TC transport in cLPM vesicles were significantly inhibited
by cycloheximide-treatment (2 mg/kg). oPRL (300 [mu]g/day, iv 7-days)
increased expression of Ca2+, Mg2+ ecto-ATPase mRNA 6-fold and
protein 23-fold, but had no effect on the expression of P
-glycoprotein (mdr1b and mdr2) mRNA. Thus, the increase in ATP
-dependent transport in cLPM vesicles due to oPRL-treatment accounts
for the increased TC SRm in the perfused liver. The oPRL-mediated
increased TC transport may be associated with increased expression of
proteins related to bile acid transport.
Received 25 August 1995; accepted in final form 9 July 1996.
APS Manuscript Number G371-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996