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

Background: 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.Methods: Forty five female Sprague-Dawley rats (Initial body mass: 169.25±9gr 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 carry-ing a load suspended from the tail and the weight increased progressively. Real-time PCR and Immunohistochemistry techniques were used to measure gene expression leve-ls and myosin heavy chain (MyHC) composition, respectively.Results: 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 respecti-vely). 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).Conclusion: However, resistance training effects on sarcomeric proteins development, these results showed no effect of resistance training on alpha-actinins-3 levels. Althou-gh alpha-actinins-3 has an important function to produce and progress of force in sarco-mere, but didn't changed significantly in response to resistance training