title: Effects of thyroid hormone administration on skeletal muscle mitochondria.
abstract: The effects of thyroid hormone administration on the levels of a number of mitochondrial markers were measured in skeletal muscle and liver of normal rats. Injection of 18 mug of L-thyroxine (T4) per 100 g body wt every 4th day for 3 wk had no effect on the concentrations of cytochrome c, on citrate synthase activity, or on respiratory capacity of skeletal muscle. Injection of 200 mug of L-triiodothyronine (T3) daily for 5 days, or feeding 23 mg T4 and 7 mg T3/kg of diet for 2 wk, resulted in thyrotoxicosis and large increases in the activity of hepatic alpha-glycerophosphate dehydrogenase and other mitochondrial markers; however, the levels of activity of mitochondrial marker enzymes in gastrocnemius and quadriceps muscles were not significantly changed. Only when rats were fed 3 mg T4 and 1 mg T3/kg diet for a 6-wk period did we observe an increase in skeletal muscle mitochondrial markers. Thus, thyroxine treatment must be sufficiently prolonged if it is to be used as a tool for studying skeletal muscle mitochondrial biogenesis.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D003574:Cytochrome c Group / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D003576:Electron Transport Complex IV / Q000378:metabolism; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects; D008931:Mitochondria, Muscle / Q000187:drug effects* / Q000201:enzymology; D010101:Oxygen Consumption / Q000187:drug effects; D011506:Proteins / Q000032:analysis; D051381:Rats; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013963:Thyroid Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; D011506:Proteins; D013963:Thyroid Hormones; D014284:Triiodothyronine; D005993:Glycerolphosphate Dehydrogenase; D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D013974:Thyroxine