Effect of a Combined Trenbolone Acetate and Estradiol Implant on Steady-State IGF-I mRNA Concentrations in the Liver of Wethers and the Longissimus Muscle of Steers

B. J. Johnson, M. E. White, M. R. Hathaway, C. J. Christians, W. R. Dayton

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

Treatment of lambs (initial BW 28 kg) for 24 d with a combined implant containing 40 mg of trenbolone acetate (TBA) and 8 mg of estradiol (E2) increased ADG 25% (P < .05, n = 8) and feed efficiency 23% (P < .05, n = 2) compared with unimplanted lambs. By d 3 following implantation, sera from wethers implanted with TBA + E2 showed 32% (307 vs 233 ng/mL) increases (P < .001, n = 8) in IGF-I concentration compared with sera from unimplanted wethers. This increase was maintained throughout the entire 24-d study. Steady-state hepatic IGF-I mRNA levels were increased approximately 150% in implanted lambs compared with unimplanted lambs (P < .05, n = 4). These data suggest that liver may be the source of at least part of the increased circulating IGF-I in TBA + E2-implanted sheep. In steers implanted with Revalor-S (120 mg of TBA and 24 mg of E2) for 40 d, the steady-state concentration of IGF-I mRNA in the longissimus muscle was 68% greater than in the longissimus muscle of unimplanted steers (P = .013, n = 4). Consequently, increased local production of IGF-I by muscle tissue may play a role in increasing circulating IGF-I concentrations as well as an autocrine or paracrine role in stimulating muscle growth in steers implanted with Revalor-S.

Original languageEnglish
Pages (from-to)491-497
Number of pages7
JournalJournal of animal science
Volume76
Issue number2
DOIs
StatePublished - Feb 1998

Keywords

  • Estradiol
  • Insulin-like Growth Factor I
  • Liver
  • Muscles
  • Trenbolone

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