[Changes in ACTN3 gene expression and fiber type composition in flexor hallucis longus muscle after eight weeks progressive resistance training in Sprague-Dawley rats]

ABSTRACT

Alpha-actinins are located in the skeletal muscle Z-line and form actin-actin cross-links. It belongs to a highly conserved family of actin-binding proteins- the spectrin superfamily, which also contains the spectrins and dystrophin. Mammalian skeletal muscle has two isoforms alpha-actinins-2 and alpha-actinins-3. However, the response of alpha-actinins to exercise training is little understood. This study examined the effects of 8 weeks of resistance training on muscle mass, ACTN3 [alpha-actinins-3] gene expression levels and fiber type composition in the flexor hallucis longus [FHL] muscle. Forty five female Sprague-Dawley rats [Initial body mass 169.25 +/- 9 gr age 3 month] were obtained and assigned to a control [C; n=18] or exercise training [T; n=22] and pilot [P; n=5] groups. The resistance training consisted of climbing a ladder carrying a load suspended from the tail and the weight increased progressively. Real-time PCR and Immunohistochemistry techniques were used to measure gene expression levels and myosin heavy chain [MyHC] composition, respectively. Following 8 weeks of training, we observed significant increase in absolute muscle mass in FHL [P=0.01]. Results showed that no significant difference was found in ACTN3 gene expression levels between training and control groups [P=0.852 respectively]. Also, Pearson coefficient didn't indicated any significant relationships in gene expression and Fiber type IIX in response to resistance training in FHL [r=0.12]. However, resistance training effects on sarcomeric proteins development, these results showed no effect of resistance training on alpha-actinins-3 levels. Although alpha-actinins-3 has an important function to produce and progress of force in sarcomere, but didn't changed significantly in response to resistance training