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 Depreux, F. F. S. Articles by Gerrard, D. E. Search for Related Content PubMed PubMed Citation Articles by Depreux, F. F. S. Articles by Gerrard, D. E.

Paylean alters myosin heavy chain isoform content in pig muscle¹

Department of Animal Sciences, Purdue University, West Lafayette, IN 47907

⁴ Correspondence:
Smith Hall (phone: 765-494-8280; fax: 765-494-6816; E-mail:
dgerrard{at}purdue.edu).

Feeding ß-adrenergic agonists promotes muscle growth. Early histological techniques failed to show precisely how feeding ractopamine-HCl (Paylean) alters muscle growth in pigs. To understand these effects, an indirect enzyme-linked immunosorbent assay (ELISA) was used to determine the abundance of each adult skeletal muscle myosin heavy chain isoform, one means of assigning muscle fiber type, in fast and slow muscles of pigs fed Paylean. Sixty growing pigs (85 kg) were randomly assigned to three Paylean doses (0, 20, or 60 ppm). At 3, 7, 14, 28, and 42 d of treatment, four pigs per dose were harvested and white (WST) and red (RST) semitendinosus and longissimus (LM) muscles were removed and processed, and myosin heavy chain was quantified by ELISA. Feeding Paylean enhanced (P < 0.05) pigs’ average daily gain. Muscle myosin heavy chain (slow, 2A, 2AX, and 2B) composition differed (P < 0.05) across muscles. Compared with LM, RST contained approximately five times more (P < 0.0001) slow and type 2A myosin heavy chain and three times more 2AX myosin heavy chain but nearly undetectable amounts of 2B myosin heavy chain. Myosin heavy chain composition of the WST closely resembled that of the LM (i.e., greater 2AX and 2B and less slow and 2A). After 42d of 60 ppm Paylean, the amount of slow, 2A, and 2AX myosin heavy chain decreased (P < 0.05) across the three muscles whereas the amount of 2B myosin heavy chain increased (P < 0.05). In contrast, relative amounts of 2A and 2AX myosin heavy chain increased (P < 0.05) in muscle of control pigs at 42d. Changes associated with the 20-ppm dose were intermediate to and different from (P < 0.05) control and 60 ppm treatments. Correlations (P < 0.05) among various myosin heavy chain within muscles suggest that slow, type 2A, and 2X decrease with increases in 2B myosin heavy chain. These data show that administration of Paylean affects myosin heavy chain isoform composition in a time- and dose-dependent manner and provides a mechanism of action for Paylean altering animal growth.

Key Words: ß-Adrenergic Agonists • Muscle Fibers • Myosins

This article has been cited by other articles:

				A. M. Gunawan, B. T. Richert, A. P. Schinckel, A. L. Grant, and D. E. Gerrard Ractopamine induces differential gene expression in porcine skeletal muscles J Anim Sci, September 1, 2007; 85(9): 2115 - 2124. [Abstract] [Full Text] [PDF]

				J. M. Gonzalez, J. N. Carter, D. D. Johnson, S. E. Ouellette, and S. E. Johnson Effect of ractopamine-hydrochloride and trenbolone acetate on longissimus muscle fiber area, diameter, and satellite cell numbers in cull beef cows J Anim Sci, August 1, 2007; 85(8): 1893 - 1901. [Abstract] [Full Text] [PDF]

				T. S. Stahly, N. H. Williams, T. R. Lutz, R. C. Ewan, and S. G. Swenson Dietary B vitamin needs of strains of pigs with high and moderate lean growth J Anim Sci, January 1, 2007; 85(1): 188 - 195. [Abstract] [Full Text] [PDF]