title: Effect of corticosterone on rate of myofibrillar protein breakdown in adult male rats.
abstract: The urinary excretion of N tau-methylhistidine (3-methylhistidine: 3-Mehis) was measured in 280-g intact and adrenalectomized (AdX) male rats to assess the effect of corticosterone on the rate of myofibrillar protein breakdown near the end of their growth period. Urinary outputs of urea-N and creatinine were also determined. Rats were given either vehicle or 10 mg of corticosterone subcutaneously/100 g body weight/day during 8 days. At the termination of the experiment, samples of blood were taken for insulin and corticosterone determination, and the livers and selected hind limb muscles were excised and weighed. As compared to either intact or AdX rats receiving vehicle injection, significant (p less than 0.05) and extensive reductions in body weight and muscle weight were found in the AdX rats receiving the steroid, whereas there was a significant increase (p less than 0.05) in liver weight, and in insulin and corticosterone plasma concentrations. Urinary output of 3-Mehis increased considerably during the first 4 days of corticosteroid treatment and then declined. This later adaptive change may account for findings by some authors of a lack of response of muscle protein breakdown some days after commencement of steroid treatment. It is concluded that mature rats, like growing rats, undergo acceleration in rate of myofibrillar protein breakdown when given high doses of corticosteroids, and consequently, that the effects on muscle metabolism are not an indirect result of suppression of growth.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D001835:Body Weight; D003345:Corticosterone / Q000494:pharmacology*; D003404:Creatinine / Q000652:urine; D007700:Kinetics; D008297:Male; D008762:Methylhistidines / Q000652:urine; D009124:Muscle Proteins / Q000378:metabolism*; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014508:Urea / Q000652:urine
chemical_list: D008762:Methylhistidines; D009124:Muscle Proteins; D014508:Urea; D003404:Creatinine; C028118:3-methylhistidine; D003345:Corticosterone