Triiodothyronine regulation of multiple rat hepatic genes: Requirement for ongoing protein synthesis

Abstract

We have examined the role of rapidly turning over proteins in the T3 regulation of multiple rat hepatic genes. T3 induction of the rapidly responsive mRNA-S14 was markedly inhibited by cycloheximide (1 mg/ 100 g BW) or emetine (3 mg/100 g) injected ip 30 min before T3 (mRNA-S14 concentration was only 35% of that in T3-treated controls 8.5 h after administration of either protein synthesis inhibitor, P < 0.01). Cycloheximide exhibited a similar effect on each of five other more slowly responsive T3 regulated genes. When cycloheximide was given 10 h after T3 the expected T3-induced rise of mRNA-S7 activity was completely prevented, and for mRNA-S4 activity the anticipated rise was blunted to 4..