The effects of zilpaterol hydrochloride and chromium propionate on bovine muscle satellite cells and preadipocytes

Numerous feed additives have been used in the beef industry for enhancing muscle growth, improving immune efficiency, and increasing carcass quality. Zilpaterol hydrochloride (ZH), a beta-2 adrenergic agonist, has been used for enhancing muscle growth in feedlot cattle. Chromium propionate has shown to increase immune efficiency in all livestock species, increase pork quality, and increase milk yield in dairy cattle. The objectives of these in vitro experiments were to determine the effects of each compound on enzymes and/or growth factors in bovine muscle satellite cells (BSC) and/or intramuscular and subcutaneous preadipocytes.
In the ZH experiments, insulin-like growth factor I (IGF-I) mRNA abundance increased in cells treated with ZH for 48 h and 120 h. A β2-adrenergic receptor antagonist (ICI) was used to block the effects of ZH. The addition of ICI attenuated the effect of ZH on IGF-I mRNA abundance. Myosin heavy chain (MHC) isoform I and MHC IIX mRNA expression was increased in cells treated with ZH for 120 h. This effect was ameliorated when ICI was added to the media. When cells were treated with ZH for 48 h there was no effect of ZH on MHC I or MHC IIX mRNA abundance. Indicating that MHC isoform abundance may be affected by duration of treatment. In the chromium propionate experiments, glucose transporter type 4 (GLUT4) mRNA abundance tended to increase after 144 h of treatment of 1 µM or 10 µM chromium propionate in intramuscular preadipocytes and increased in subcutaneous preadipocytes. Relative mRNA abundance for PPARγ increased when differentiation media was added for intramuscular and subcutaneous preadipocytes. In BSC, GLUT4/GAPDH protein abundance decreased in a dose-dependent matter when chromium propionate was added to the cultures. Results indicated that ZH and chromium propionate affect enzymes and growth factors important to muscle and adipose tissue growth.