The regulatory effects of thyroid hormone on the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase.
The effects of 3, 3', 5-triiodothyronine (T3) on 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were evaluated in the C100 baby hamster kidney cell line. Cells cultured in Minimal Essential Medium (MEM) were supplemented with 10% thyroid hormone-depleted fetal bovine serum (THDS-MEM) and had a 70.1% lower level of HMG-CoA reductase activity than the cells grown in a medium supplemented with fetal bovine serum (FBS). When T3 was added to THDS-MEM, the reduction of the reductase activity was blocked in a dose-dependent manner. In the cells grown in THDS-MEM for 48 hours, T3 (10(-6) M) treatment rapidly increased HMG-CoA reductase activity, achieving the control level six hours after treatment. Such effects of T3 were blocked by actinomycin D (5 microg/ml) or cycloheximide (10 microg/ml). The transcriptional rate of the HMG-CoA reductase gene did not change significantly regardless of the presence of T3, while T3 inhibited the 25-hydroxycholesterol-mediated decay of the reductase mRNA significantly. Our results show that T3-dependent regulation of HMG-CoA reductase activity, via the de novo synthesis of the reductase enzyme, seems to be mediated at least partially by the stabilization of HMG-CoA reductase mRNA.
Choi
J W
JW
Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea. jwchoiphar@yumc.yonsei.ac.kr
Choi
H S
HS
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D006888:Hydroxycholesterols / Q000494:pharmacology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014284:Triiodothyronine / Q000494:pharmacology / Q000502:physiology*
D006888:Hydroxycholesterols; D012333:RNA, Messenger; D014284:Triiodothyronine; C007997:25-hydroxycholesterol; D006903:Hydroxymethylglutaryl CoA Reductases