HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pampusch, M. S. Articles by Dayton, W. R. Search for Related Content PubMed PubMed Citation Articles by Pampusch, M. S. Articles by Dayton, W. R.

Time course of changes in growth factor mRNA levels in muscle of steroid-implanted and nonimplanted steers^1,2,3

M. S. Pampusch^*, B. J. Johnson, M. E. White^*, M. R. Hathaway^*, J. D. Dunn, A. T. Waylan and W. R. Dayton^*,4

^* Animal Growth and Development Laboratory, Department of Animal Science, University of Minnesota, St. Paul 55108; and and Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506

⁴ Correspondence: 348 ABLMS, 1334 Eckles Ave. (phone: 612-624-2234; fax: 612-624-3677; E-mail: wdayton{at}umn.edu).

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.

Key Words: Estradiol • Implant • Insulin-Like Growth Factor-I • Muscle • Steer • Trenbolone Acetate

This article has been cited by other articles:

				M. S. Pampusch, M. E. White, M. R. Hathaway, T. J. Baxa, K. Y. Chung, S. L. Parr, B. J. Johnson, W. J. Weber, and W. R. Dayton Effects of implants of trenbolone acetate, estradiol, or both, on muscle insulin-like growth factor-I, insulin-like growth factor-I receptor, estrogen receptor-{alpha}, and androgen receptor messenger ribonucleic acid levels in feedlot steers J Anim Sci, December 1, 2008; 86(12): 3418 - 3423. [Abstract] [Full Text] [PDF]

				S. J. Winterholler, G. L. Parsons, D. K. Walker, M. J. Quinn, J. S. Drouillard, and B. J. Johnson Effect of feedlot management system on response to ractopamine-HCl in yearling steers J Anim Sci, September 1, 2008; 86(9): 2401 - 2414. [Abstract] [Full Text] [PDF]

				W. R. Dayton and M. E. White Cellular and molecular regulation of muscle growth and development in meat animals J Anim Sci, April 1, 2008; 86(14_suppl): E217 - E225. [Abstract] [Full Text] [PDF]

				K. Y. Chung and B. J. Johnson Application of cellular mechanisms to growth and development of food producing animals J Anim Sci, April 1, 2008; 86(14_suppl): E226 - E235. [Abstract] [Full Text] [PDF]

				E. K. Sissom, C. D. Reinhardt, J. P. Hutcheson, W. T. Nichols, D. A. Yates, R. S. Swingle, and B. J. Johnson Response to ractopamine-HCl in heifers is altered by implant strategy across days on feed J Anim Sci, September 1, 2007; 85(9): 2125 - 2132. [Abstract] [Full Text] [PDF]

				E. K. Sissom, C. D. Reinhardt, and B. J. Johnson Melengestrol acetate alters muscle cell proliferation in heifers and steers J Anim Sci, November 1, 2006; 84(11): 2950 - 2958. [Abstract] [Full Text] [PDF]

				R. G. Mateescu and M. L. Thonney Effect of testosterone on insulin-like growth factor-I, androgen receptor, and myostatin gene expression in splenius and semitendinosus muscles in sheep J Anim Sci, April 1, 2005; 83(4): 803 - 809. [Abstract] [Full Text] [PDF]

				Y. K. Kim, H. Choi, and K. H. Myung Effects of propylene glycol on carcass traits and its related gene expression in Korean native steers J Anim Sci, February 1, 2005; 83(2): 344 - 349. [Abstract] [Full Text] [PDF]

				J. D. Dunn, B. J. Johnson, J. P. Kayser, A. T. Waylan, E. K. Sissom, and J. S. Drouillard Effects of flax supplementation and a combined trenbolone acetate and estradiol implant on circulating insulin-like growth factor-I and muscle insulin-like growth factor-I messenger RNA levels in beef cattle J Anim Sci, December 1, 2003; 81(12): 3028 - 3034. [Abstract] [Full Text] [PDF]