Time course of changes in growth factor mRNA levels in muscle of steroid-implanted and nonimplanted steers

• Published in: Journal of animal science 2003-11, Vol.81 (11), p.2733-2740
• Main Authors: Pampusch, M.S, Johnson, B.J, White, M.E, Hathaway, M.R, Dunn, J.D, Waylan, A.T, Dayton, W.R
• Format: Article
• Language: English
• Subjects: Animal productions; Animals; Base Sequence; Biological and medical sciences; Cattle - metabolism; cell proliferation; Drug Combinations; Drug Implants; dry matter intake; Energy Intake - drug effects; Estradiol - administration & dosage; Estradiol - pharmacology; feed conversion; Fundamental and applied biological sciences. Psychology; Growth Substances - genetics; Growth Substances - metabolism; hepatocyte growth factor; Hepatocyte Growth Factor - genetics; Hepatocyte Growth Factor - metabolism; Insulin-Like Growth Factor Binding Protein 3 - genetics; Insulin-Like Growth Factor Binding Protein 3 - metabolism; insulin-like growth factor I; Insulin-Like Growth Factor I - genetics; Insulin-Like Growth Factor I - metabolism; longissimus muscle; Male; messenger RNA; Muscle, Skeletal - metabolism; Myostatin; Polymerase Chain Reaction - methods; Polymerase Chain Reaction - veterinary; quantitative polymerase chain reaction; Random Allocation; RNA, Messenger - metabolism; steers; Terrestrial animal productions; Time Factors; Transforming Growth Factor beta - genetics; Transforming Growth Factor beta - metabolism; Trenbolone Acetate - administration & dosage; Trenbolone Acetate - analogs & derivatives; Trenbolone Acetate - pharmacology; Vertebrates
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/2003.81112733x

We used a muscle biopsy technique in conjunction with real-time PCR analysis to examine the time course of changes in muscle IGF-I, IGFBP-3, myostatin, and hepatocyte growth factor (HGF) mRNA in the longissimus muscles of Revalor-S-implanted and nonimplanted steers on d 0, 7, 12, and 26 after implantation (nine steers/treatment group). Administration of a Revalor-S implant increased (P < 0.01) ADG and improved (P < 0.05) feed efficiency, 36 and 34 %, respectively, compared with steers that received no implant during the 26-d trial. Daily dry matter intake did not differ (P > 0.15) between nonimplanted and implanted steers. Steers receiving the Revalor-S implant had increased (P < 0.001) circulating IGF-I concentrations compared with nonimplanted steers. The longissimus muscles of steers receiving the Revalor-S implant contained increased (P < 0.001) IGF-I mRNA levels compared with longissimus muscles of nonimplanted steers over the 26-d duration of the study. Longissimus muscle IGF-I mRNA levels in implanted steers were increased (P < 0.003) relative to d-0 concentrations on d 7 and 12 (101% and 128%, respectively), and by d 26, longissimus muscle mRNA levels were more than three times (P < 0.0001) those in the longissimus muscles of the same steers on d 0. There was no treatment effect on the level of IGFBP-3, myostatin, or HGF mRNA in the longissimus muscle at any time point; however, levels of IGFBP-3, myostatin, and HGF mRNA increased with time on feed. Based on current and previous studies, we hypothesize that the increased IGF-I level in muscle of implanted steers by d 7 of implantation stimulates satellite cell proliferation and maintains a high number of proliferating satellite cells at a point in the growth curve where satellite cell numbers and activity are normally dropping off. This would prolong the period of rapid muscle growth, resulting in the observed increased rate and efficiency of muscle deposition in implanted steers.