title: Effect of a synthetic antimicrobial agent on the rates of synthesis and degradation of liver and skeletal muscle proteins in growing rats.
abstract: A double isotope technique was used to evaluate the effects of a synthetic antimicrobial compound (carbadox) upon the synthesis and degradation of rat liver and muscle proteins. Trials 1 and 2 used, respectively, 20 and 12 male Sprague-Dawley rats with average initial weights of 75 and 81 g. A 16% crude protein corn-soybean diet without or with carbadox (55 ppm) was fed. Rats were randomly assigned to diets which were fed 10 days prior to the initial isotope (14C-lysine) injection. The second isotope injection (3H-lysine) was made 3 days after the 14C-lysine injection in trial 1, 6 days in trial 2. Four hours after the second injection, the rats were killed and the right and left quadriceps and a sample of liver were removed. Total protein from the right quadriceps was prepared via a boiling trichloroacetic acid (TCA) extraction procedure. The left quadriceps was separated into myofibrillar and sarcoplasmic protein fractions via a KCl salt gradient. In both trials, gains were similar across treatments, but markedly reduced during the injection periods. Gain/feed prior to injection was greater (P less than 0.05) for carbadox-fed rats. In both trials right quadriceps 3H-incorporation (expressed as 3H cpm/mg protein) and relative degradation (3H cpm/14C cpm) were not affected by dietary carbadox. The sarcoplasmic and myofibrillar protein fractions were also not significantly affected. However, in both trials liver protein 3H-incorporation was enhanced (P less than 0.025) by carbadox, while liver protein degradation was affected (P less than 0.001) only in trial 2.
mesh_terms: D000818:Animals; D002218:Carbadox / Q000494:pharmacology*; D006128:Growth; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D011506:Proteins; D011810:Quinoxalines; D002218:Carbadox