Examining the effects of estradiol, trenbolone acetate, or polyamines on bovine satellite cell differentiation

The mechanism through which anabolic implants improve skeletal muscle growth of beef animals is incompletely understood. Polyamines (PA) are bioactive amino acid derivatives that act as potent growth stimulants. The objective of this study was to determine effects of anabolic implants, PA and their precursors on bovine satellite cell (BSC) differentiation. Primary BSC were cultured to approximately 80% confluency, at which time they were induced to differentiate in the presence of 3% horse serum (Con) and treated with 10nM TBA, 10 nM E2, or 10nM TBA and 10 nM E2 (ETBA), 10 mM methionine (Met), 8 mM ornithine (Orn), 2 mM putrescine (Put), 1.5 mM spermidine (Spd) or 0.5 mM spermine (Spe). Total mRNA was isolated 0, 2, 4, 8, 12, 24, or 48 h post-treatment and abundance of paired box transcription factor 7 (Pax7) and myogenic differentiation factor (MyoD) were analyzed. Treatment with the hormones (TBA, E2, or ETBA) and PA (Orn, Put, Spd, and Spe) increased (P < 0.05) abundance of MyoD 4 h post-treatment when compared to Con cultures. However, 24 h posttreatment, MyoD abundance was decreased in the presence of hormone treatments when compared to the Con, while the PA treatments increased (P < 0.05) abundance of MyoD when compared to the Con cultures. Treatment with either the hormones or PA had no effect (P > 0.05) on Pax7 abundance at 2, 4, 8, 12, 24, or 48 h post-treatment when compared to Con cultures (P > 0.05). These results indicate that treatment with PA or hormones increases abundance of MyoD, though temporally different indicating that these two classes of growth promoters impact differentiation via alternate physiological pathways. Additional research is underway in order to determine the effects of both PA and hormones on differentiation of primary BSC.