Muscle type-specific responses of myoD and calpain 3 expression to recombinant porcine growth hormone in the pig

Abstract

Sixteen castrated male Large White 3 Landrace pigs were employed to investigate the muscle type-specific changes of gene expression in response to recombinant porcine growth hormone (rpGH) administration. Pigs were injected intramuscularly with rpGH (4 mg/day, n 5 8) or saline (n 5 8) for 28 days. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the mRNA abundance of genes related to muscle growth in longissimus dorsi (LD) and semitendinosus (ST) muscles. Myofibre-type composition was characterised by the ratio of the expression of myosin heavy chain (MyHC) 1, 2a or 2b relative to 2x. The results showed that the relative myofibre-type composition of neither LD nor ST was affected by rpGH administration. rpGH administration did not induce significant changes in the abundances of myostatin and myogenin mRNA in both types of muscle. MyoD and calpain 3 mRNA were significantly increased after rpGH treatment in ST muscle, whereas the difference was not significant in LD muscle. A tendency of down-regulation was observed for PGC-1a mRNA expression in ST muscle of rpGH-treated group (P 5 0.16). These results suggest that myoD, calpain 3 and probably PGC-1a may be involved in the mechanism of exogenous GH action on skeletal muscle growth; rpGH up-regulates mRNA expression of myoD and calpain 3 in a muscle type-specific manner, being more remarkable in ST than in LD, whereas no influences of rpGH on the mRNA expression of myostatin and myogenin were detected.

Effect of L‐lysine on expression of selected genes, serum concentration of amino acids, muscle growth and performance of growing pigs

“…Muscle in pigs is formed by four different types of fibres designated by their predominant MyHC isoform (I, IIa, IIx and IIb; Yang et al., ). These MyHC isoforms possess particular metabolic and contractile characteristics, and are differently distributed among muscles, suggesting that MyHC distribution is related to their function (Lefaucheur et al., ).…”

“…In agreement with adaptive theory of Hatzoglou et al (2004), the expression of CAT-1 in the SM tended to be approximately threefold higher in pigs fed the Lys DEF diet, indicating a lower SC of Lys, as compared to pigs fed the ADE diet. Muscle in pigs is formed by four different types of fibres designated by their predominant MyHC isoform (I, IIa, IIx and IIb;Yang et al, 2007). These MyHC isoforms possess particular metabolic and contractile characteristics, and are differently distributed among muscles, suggesting that MyHC distribution is related to their function (Lefaucheur et al, 2002).…”

“…Myosin is the most abundant protein in skeletal muscle (Czerwinski and Martin, 1994;Lefaucheur et al, 2002), which is composed of several myofibre types (Schiaffino and Reggiani, 1994). In pigs, muscle myofibres contain four different myosin heavy chain (MyHC) isoforms (I, IIa, IIx and IIb;Yang et al, 2007). MyHC IIb fibres are the most prominent in pigs and appear to be the determining fibre contributing to the differential growth of muscles (Wimmers et al, 2008).…”