title: Posttranslational inhibition of Ito cell type I collagen production by triiodothyronine.
abstract: Increased Ito cell collagen production occurs during in vivo liver fibrogenesis. Regulation of the overproduction of collagen was studied in cultured rat hepatic Ito cells, which resemble the myofibroblast associated with liver fibrosis. Previous studies suggest that the steroid hormones, retinoic acid, and glucocorticoids may have antifibrogenic properties in vitro and in vivo when used at pharmacological doses. Their potential roles at physiological levels are not well understood. The current study examined the potential regulation of the overproduction of type I collagen in cultured rat hepatic Ito cells by another steroid hormone, 3,5,3'-triiodo-L-thyronine (T3). T3 induced a 3.4-fold reduction in type I collagen production. The effect was dose dependent and was maximal with physiological levels of T3 (10(-9) M). The effect of T3 was independent of any suppression in total protein synthesis. The mechanism of the suppressive effect of T3 on collagen production was explored and was found to be at a posttranslational level. This study suggests that the inhibitory effects of T3 on type I collagen production are likely caused by enhanced intracellular turnover of type I collagen.
authors.affiliation: Department of Medicine, University of Chicago, Illinois 60637.
authors.forename: T W
authors.initials: TW
authors.lastname: Lissoos
authors.forename: D W
authors.initials: DW
authors.lastname: Beno
authors.forename: B H
authors.initials: BH
authors.lastname: Davis
mesh_terms: D000818:Animals; D002455:Cell Division; D003094:Collagen / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D011392:Proline / Q000378:metabolism; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D012333:RNA, Messenger; D014284:Triiodothyronine; D003094:Collagen; D011392:Proline