Aim: To examine the regulatory effect of bile acid level on bile acid
synthesis in the liver. Methods: The portal branch perfusing left late
ral and median lobes of the liver was ligated in rats and the activiti
es of hepatic microsomal cholesterol 7 alpha-hydroxylase, the rate-lim
iting enzyme of bile acid synthesis, 3-hydroxy-3-methylglutaryl coenzy
me A (HMG-CoA) reductase, and intrahepatic concentrations of cholester
ol and bile acids were determined in the liver lobes deprived of and s
upplied with portal blood on Days 0, 1, 2, 4, and 7 after selective po
rtal vein ligation (SPVL). Results: In the portal vein (PV)-ligated lo
bes, liver weight decreased, hepatic cholesterol concentration was unc
hanged, and microsomal cholesterol concentration increased after SPVL.
In the PV-nonligated lobes, liver weight increased, hepatic cholester
ol concentration increased, and microsomal cholesterol concentration w
as unchanged. There were no significant differences in the activities
of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase among the PV-
ligated and PV-nonligated lobes and the sham-operated controls. Intrah
epatic bile acid level increased significantly in the PV-nonligated lo
bes for 4 days after SPVL, whereas those were essentially constant in
the PV-ligated and the sham-operated control liver. Despite significan
t changes in the concentrations of intrahepatic cholesterol and bile a
cid, no significant correlations were observed between these concentra
tions and the activities of cholesterol 7 alpha-hydroxylase. Conclusio
ns: SPVL causes atrophy and hypertrophy of the PV-ligated and nonligat
ed liver lobes, respectively, without any significant changes in chole
sterol and bile acid synthesis. Intrahepatic concentrations of bile ac
ids and cholesterol have no regulatory effect on cholesterol 7 alpha-h
ydroxylase activity in the SPVL rat model. (C) 1997 Academic Press.