title: Appearance of atypical 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid in spgp knockout mice.
abstract: Bile formation and its canalicular secretion are essential functions of the mammalian liver. The sister-of-p-glycoprotein (spgp) gene was shown to encode the canalicular bile salt export protein, and mutations in spgp gene were identified as the cause of progressive familial intrahepatic cholestasis type 2. However, target inactivation of spgp gene in mice results in nonprogressive but persistent cholestasis and causes the secretion of unexpectedly large amounts of unknown tetrahydroxylated bile acid in the bile. The present study confirms the identity of this tetrahydroxylated bile acid as 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid. The data further show that in serum, liver, and urine of the spgp knockout mice, there is a significant increase in the concentration of total bile salts containing a large amount of tetrahydroxy-5 beta-cholan-24-oic acid. The increase in total bile acids was associated with up-regulation of the mRNA of cholesterol 7 alpha-hydroxylase in male mice only. It is suggested that the lower severity of the cholestasis in the spgp knockout mice may be due to the synthesis of 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid, which neutralizes in part the toxic effect of bile acids accumulated in the liver.
authors.affiliation: Department of Pharmacology, Universitè de Montréal and Centre de Recherche de l'Hôpital Sainte-Justine, Montréal, Canada.
authors.forename: Shahid
authors.initials: S
authors.lastname: Perwaiz
authors.forename: Dana
authors.initials: D
authors.lastname: Forrest
authors.forename: Diane
authors.initials: D
authors.lastname: Mignault
authors.forename: Beatriz
authors.initials: B
authors.lastname: Tuchweber
authors.forename: M James
authors.initials: MJ
authors.lastname: Phillip
authors.forename: Renxue
authors.initials: R
authors.lastname: Wang
authors.forename: Victor
authors.initials: V
authors.lastname: Ling
authors.forename: Ibrahim M
authors.initials: IM
authors.lastname: Yousef
mesh_terms: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000818:Animals; D001646:Bile / Q000737:chemistry; D001647:Bile Acids and Salts / Q000032:analysis / Q000097:blood / Q000652:urine; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D002793:Cholic Acids / Q000032:analysis* / Q000097:blood / Q000737:chemistry* / Q000652:urine; D005260:Female; D005704:Gallbladder / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D017353:Gene Deletion; D008099:Liver / Q000737:chemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; C490549:Abcb11 protein, mouse; D001647:Bile Acids and Salts; D002793:Cholic Acids; D012333:RNA, Messenger; C474453:tetrahydroxy-5-cholan-24-oic acid; D002790:Cholesterol 7-alpha-Hydroxylase