Journal of cellular physiology
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Comparative Study
IGF-I mRNA levels in bovine satellite cell cultures: effects of fusion and anabolic steroid treatment.
Androgenic and estrogenic steroids enhance muscle growth in a number of species; however, the mechanism by which anabolic steroids enhance muscle growth is not known. Castrated male cattle (steers) provide a particularly good model system in which to study the effects of anabolic steroids on muscle growth because they respond dramatically to treatment with both estrogens and androgens. The goal of this study was to determine if treatment of bovine satellite cell (BSC) cultures with 17beta-estradiol (E(2)) or trenbolone (a synthetic androgen) directly affects proliferation rate or level of mRNA for estrogen receptor (ER)-alpha, androgen receptor, and growth factors that have been shown to affect muscle growth (insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3, and myostatin). ⋯ Although, levels of IGF-I mRNA were 10-times greater (P < 0.02) in fused BSC cultures than in proliferating cultures, treatment of fused cultures for 48 h with 10 nM E(2) increased IGF-I mRNA levels (2.5-times control levels, P < 0.02). Both E(2) and trenbolone increased (3)H-thymidine incorporation rate (1.5-times control levels, P < 0.001) in BSC cultures in media containing serum from which IGFBP-3 had been removed by anti-IGFBP-3 affinity chromatography. In summary, treatment of BSC cultures with either E(2) or trenbolone increased IGF-I mRNA level and proliferation rate, thus, establishing that these steroids have direct anabolic effects on cells present in the BSC culture.