Interactive Effects of Zinc and Zilpaterol Hydrochloride on Bovine <i>β</i>-Adrenergic Receptors

The objective of this study was to determine if the addition of zinc (Zn) in combination with zilpaterol HCL (ZH) affected the interaction of ZH with the beta2-adrenergic receptor (β-AR) by altering cAMP production, gene expression, and protein abundance in cultured skeletal muscle cells. Cultures of muscle bovine satellite cells were established and treated at 120 h with: 1) 0 μM Zn/zilpaterol hydrochloride (ZH;CON);2) 0 μM Zn/10 μM ZH (ZH);3) 1 μM Zn from Zn chloride/0 μM ZH (Zn);4) 1 μM Zn from Zn chloride/10 μM ZH (ZN/ZH) in differentiation media for an additional 0, 6, 24, 48 and 96 h. Protein and mRNA were isolated and quantified at 24 and 96 h, and cAMP was measured at 0, 6, 24, 48 and 96 h. At 0, 24, 48 and 96 h, no differences (P > 0.05) were detected in cAMP production. At 6 h, Zn cells had the greatest concentration of cAMP (P < 0.05) compared to ZH treatments. No differences (P > 0.05) were detected in mRNA abundance at 24 h. At 96 h, 0 μM Zn/10 μM ZH cells had an increased abundance of myosin heavy chain (MHC)-I mRNA (P < 0.05) compared to CON. Furthermore, ZH had a greater abundance of MHC-IIX mRNA (P < 0.05) and a tendency for a greater abundance of IGF-1 mRNA (P < 0.15) compared to CON and ZN/ZH. No differences (P > 0.05) were detected in the protein abundance of β1AR and the β2AR. These results indicated Zn and ZH in combination did not have an additive effect on β2-AR function as indicated by cAMP concentrations.