title: Triiodothyronine accelerates maturation of bile acid metabolism in infant baboons.
abstract: We tested the hypothesis that triiodothyronine (T3) treatment accelerates the early postnatal maturation of bile acid metabolism in the baboon. Infant baboons were implanted with 21-day-release pellets containing T3 (n = 12), a placebo pellet (n = 6), or no pellet (n = 13). T3 treatment increased plasma T3 concentrations from 3.0 to 5.0 nmol/l between birth and 15 wk of age. At 15 wk of age, bile acid pool sizes, fractional turnover rates (FTR), and synthetic rates were determined by an isotope-dilution method with 3H- and 14C-labeled cholic (CA) and chenodeoxycholic acid (CDCA). T3 treatment increased CA pool size by 47% and CA synthetic rate by 37% but did not significantly affect CDCA pool size or synthetic rate. Consequently CA-to-CDCA pool size ratio (0.77 vs. 0.42) and biliary CA-to-CDCA concentration ratio (0.88 vs. 0.46) were higher in the T3-treated infants than in combined placebo-treated and nontreated control infants. T3 treatment did not affect the bile acid glycine-to-taurine conjugate ratio, CA FTR, or CDCA pool size, FTR, and synthetic rate. T3 treatment lowered plasma high-density lipoprotein fraction 2 and 3 cholesterol concentrations by 22 and 40%, respectively. T3 treatment also increased hepatic low-density lipoprotein receptor mRNA levels but did not affect plasma low-density lipoprotein cholesterol concentrations. We conclude that modest elevation of plasma T3 during the preweaning period increases the CA-to-CDCA ratio at the end of the preweaning period to near adult values.
authors.affiliation: Department of Physiology and Medicine, Southwest Foundation for Biomedical Research, San Antonio 78228-0147, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Lewis
authors.forename: E M
authors.initials: EM
authors.lastname: Jackson
authors.forename: G E
authors.initials: GE
authors.lastname: Mott
mesh_terms: D015065:17-Hydroxycorticosteroids / Q000652:urine; D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001646:Bile / Q000378:metabolism; D001647:Bile Acids and Salts / Q000378:metabolism*; D001835:Body Weight / Q000187:drug effects; D002635:Chenodeoxycholic Acid / Q000378:metabolism; D019826:Cholic Acid; D002793:Cholic Acids / Q000378:metabolism; D003404:Creatinine / Q000652:urine; D007700:Kinetics; D008055:Lipids / Q000097:blood; D008099:Liver / Q000378:metabolism; D010215:Papio; D012333:RNA, Messenger / Q000378:metabolism; D011973:Receptors, LDL / Q000235:genetics; D013963:Thyroid Hormones / Q000097:blood; D014284:Triiodothyronine / Q000494:pharmacology / Q000502:physiology*
chemical_list: D015065:17-Hydroxycorticosteroids; D001647:Bile Acids and Salts; D002793:Cholic Acids; D008055:Lipids; D012333:RNA, Messenger; D011973:Receptors, LDL; D013963:Thyroid Hormones; D014284:Triiodothyronine; D002635:Chenodeoxycholic Acid; D003404:Creatinine; D019826:Cholic Acid