title: Activation state of muscle satellite cells isolated from steers implanted with a combined trenbolone acetate and estradiol implant.
abstract: Muscle satellite cells were isolated from seven yearling steers implanted for 31 d with a combined implant that contained 120 mg of trenbolone acetate (TBA) and 24 mg of estradiol (E2) and from seven nonimplanted, control steers. Implanted steers had a 28% greater ADG and a 23% greater feed efficiency than did nonimplanted steers. Implanted steers had increased (P<.001) circulating IGF-I concentrations on d 6, 14, and 31 after implantation, and circulating IGF-I concentrations in control steers remained constant or decreased (P<.05) at these times. Maximum fusion percentage was greater (P< .005) in satellite cell cultures isolated from implanted steers (ISC cultures) than in satellite cell cultures isolated from control steers (NSC cultures) (72.8% vs 54.8%, respectively). Satellite cell cultures isolated from implanted steers (ISC cultures) also contained a greater (P<.001) number of myotube nuclei than did NSC cultures (7,998 nuclei/cm2 vs 5,150 nuclei/cm2, respectively). After 72 h in culture, the number of cells (corrected for plating density) was 43% greater (P<.05) in ISC cultures than in NSC cultures. [3H]Thymidine incorporation rates per 10(5) cells at 24 and 34 h after plating were greater (P<.05) in ISC cultures than in NSC cultures; however, incorporation rates did not differ at 72 h. These data indicate that TBA + E2 implantation may result in an in vivo activation of muscle satellite cell proliferation that can be detected in cell culture. This activation may play an important role in TBA + E2-enhanced muscle growth.
authors.affiliation: Department of Animal Science, University of Minnesota, St. Paul 55108, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Johnson
authors.forename: N
authors.initials: N
authors.lastname: Halstead
authors.forename: M E
authors.initials: ME
authors.lastname: White
authors.forename: M R
authors.initials: MR
authors.lastname: Hathaway
authors.forename: A
authors.initials: A
authors.lastname: DiCostanzo
authors.forename: W R
authors.initials: WR
authors.lastname: Dayton
mesh_terms: D045930:Anabolic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002417:Cattle / Q000254:growth & development*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004338:Drug Combinations; D004343:Drug Implants; D004435:Eating / Q000187:drug effects; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development*; D014204:Trenbolone Acetate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects
chemical_list: D045930:Anabolic Agents; D004338:Drug Combinations; D004343:Drug Implants; C021828:Revalor; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D014204:Trenbolone Acetate