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

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±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.

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).

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.