Quantitative Histology and MGF Gene Expression in Rats following SSC Exercise In Vivo
- Autores: Brent A. Baker, K.M.K. Rao, Robert R. Mercer
- Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 38, Nº. 3, 2006, págs. 463-471
- Idioma: inglés
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Resumen
Purpose: We investigated the effects of muscle length during stretch-shortening cycles (SSC) in vivo on changes in MGF gene expression and quantitative morphometry in rat skeletal muscle.
Methods: Dorsiflexor muscles of male Sprague-Dawley rats were exposed to seven sets of 10 SSC at 500[degrees][middle dot]s-1. Animals were randomly assigned to a long muscle length injury group (L-inj), short muscle length injury group (S-inj), or isometric group (Iso), with recoveries examined at 6 or 48 h post-injury for each group. Following exposure, animals were euthanized, and the tissue was prepared for either histology (quantitative morphometry) or RNA isolation, followed by quantitative real-time reverse transcriptase polymerase chain reaction. mRNA levels were measured for mechano-growth factor (MGF), while 18S ribosomal RNA served as the internal reference sample.
Results: Stereological measures indicative of edema and myofiber degeneration were significantly increased in the L-inj SSC group at 48 h when compared with the S-inj or Iso group. MGF mRNA was increased transiently at 6 h in the isometric group. In contrast, MGF mRNA was increased at 48 h in the S-inj, but was not increased at either time point in the L-inj group.
Conclusion: These data strongly indicate that exposure to SSC at longer muscle lengths result in greater morphometric indices of inflammation and degeneration than SSC conducted at a shorter muscle lengths or isometric contractions, at the same time that the adaptation to SSC was prolonged and, apparently, not resolved in the L-inj group that was manifested by the lack of up-regulation in MGF mRNA.
