203 - Estradiol Improves Proliferation and Protein Synthesis Rates of Primary Bovine Satellite Cells by Altering mRNA Abundance Related to Amino Acid and Micronutrient Metabolism

Abstract: Approximately 90% of beef cattle on feed in the U.S. receive an anabolic implant to improve production. The mechanisms implants operate through to improve growth have not been deciphered. Estradiol (E2) is one of the primary hormones found in anabolic implants. The objective of this study was to determine the effects of E2 on mRNA abundance of genes associated with skeletal muscle growth in proliferating and fused bovine satellite cells (BSC). To accomplish this, BSC were isolated from six backgrounded steers and cultured. Proliferation experiments used BSC cultures grown to 75% confluency, followed by treatment with 1% fetal bovine serum (FBS) or 10 nM E2 in 1% FBS. Protein synthesis experiments used cultures grown to 80% confluency, at which point cultures were induced to differentiate and treated 48-h later with serum free media (SFM) or10 nM E2 in SFM. Isolation of RNA occurred 30-min and 12-h post-treatment in both experiments. The mRNA abundance of 94 genes associated with skeletal muscle growth were examined. Treatment with E2 increased (P < 0.05) both proliferation and protein synthesis rates compared with controls. In proliferating BSC, 30-min post-treatment four genes had abundance altered (P < 0.10) by E2, while 12-h post treatment two genes had abundance altered (P < 0.10). Fused BSC, 30-min post-treatment, E2 altered (P < 0.10) abundance of five genes, while 12-h post treatment eight genes were altered (P < 0.10). A subset of significant genes include Zip8 abundance increasing (P=0.03) 30-min post-treatment in E2 treated proliferating BSC, arginase-2 abundance increasing (P=0.03) 30-min post-treatment in E2 treated fused cultures, Retinoid X Receptor-gamma abundance increasing (P=0.05) 12-h post-treatment in E2 treated proliferating BSC, and superoxide dismutase-2 abundance increasing (P=0.05) 12-h post-treatment in E2 treated fused BSC. These results indicate that E2 may improve proliferation and protein synthesis rates of BSC by altering mRNA abundance related to amino acid and micronutrient metabolism.