The effects of tri-iodothyronine on the synthesis of mitochondrial proteins in isolated rat hepatocytes.

The effects of tri-iodothyronine on mitochondrial protein synthesis have been studied in in vitro labeled, isolated rat hepatocytes. Hepatocytes were isolated from hypothyroid rats or from hypothyroid rats 24 h after injecting a single, low dose of hormone (20-30 microgram/180-230 g body weight). Tri-iodothyronine increased translation on mitochondrial ribosomes by 2-3-fold, but, under our conditions, appears to have little or not effect on the general synthesis of cytoplasmically-translated mitochondrial proteins. Electrophoretic and fluorographic analysis indicated that tri-iodothyronine stimultes labeling of the four major mitochondrially-translated peptides. The hormone appears to act by inducing a general increase in translation/transcription of mitochondrially-synthesized peptides.