Regulation of bile acid synthesis under reconstructed enterohepatic circulation in rats.
Cholesterol 7alpha-hydroxylase (CYP7A1) is regulated by bile acids through the farnesoid X receptor (FXR) mechanism in a negative feedback fashion. However, the fact that CYP7A1 is down-regulated by intraduodenal administration of bile acid, but not by intravenous administration may not be explained only by this mechanism. The aim of this study was to establish a new rat model with reconstructed or simulated enterohepatic circulation to examine if intravenous or portal administration of bile acid can regulate CYP7A1. Under biliary drainage, taurocholate (0 or 6 micromol/h/100g body weight) was administered continuously for 48h into the duodenum (ID-0/ID-6), femoral vein (IV-0/IV-6), or portal vein (IP-0/IP-6) to create a condition in which biliary bile acids were continuously lost, and a similar dose of taurocholate was supplied to the liver simultaneously. CYP7A1 activity and mRNA expression of the ID-0 group were significantly increased compared with the no treatment (NT) group. CYP7A1 activity and mRNA expression of the ID-6 group were suppressed significantly to 41 and 46% of those of the ID-0 group, respectively. In the IV-6 and IP-6 groups, however, enzyme activity and mRNA expression were decreased slightly, but the suppression was not statistically significant. The results suggested that portal as well as intravenous administration of bile acids cannot suppress bile acid synthesis as effectively as intraduodenal administration. It was concluded that an unidentified regulatory factor other than the nuclear receptors may be involved in bile acid synthesis in vivo.
Department of Surgery and Oncology, Kyushu University School of Medicine, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Masahiro
M
Nagano
Syoji
S
Kuroki
Atsushi
A
Mizuta
Masae
M
Furukawa
Mitsuhide
M
Noshiro
Kazuo
K
Chijiiwa
Masao
M
Tanaka
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis* / Q000097:blood / Q000378:metabolism; D001659:Biliary Tract / Q000378:metabolism; D001663:Bilirubin / Q000097:blood; D002408:Catheters, Indwelling; D002768:Choledochostomy; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*; D004386:Duodenum; D004764:Enterohepatic Circulation / Q000502:physiology*; D005268:Femoral Vein; D015870:Gene Expression / Q000187:drug effects; D007262:Infusions, Intravenous; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008099:Liver / Q000033:anatomy & histology / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D023421:Models, Animal; D009929:Organ Size / Q000187:drug effects; D011169:Portal Vein; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013656:Taurocholic Acid / Q000008:administration & dosage / Q000494:pharmacology
D001647:Bile Acids and Salts; D012333:RNA, Messenger; D013656:Taurocholic Acid; D007770:L-Lactate Dehydrogenase; D002790:Cholesterol 7-alpha-Hydroxylase; D000410:Alanine Transaminase; D001663:Bilirubin