AIM The family of muscle specific basic helix-loop-helix (bHLH) regulatory factors consists of MyoD, Myf-5, myogenin and MRF4. These factors contribute to the transcriptional activation of muscle genes during commitment and differentiation. A distinct role for the bHLH myogenic factors initially was suggested by their different temporal expression patterns in the somites and limbs during embryonic development. The aim of this study was to determinate time course expression of MyoD and myogenin during regeneration in muscles of different developmental origin and different rat strains. MATERIALS AND METHODS All experiments were performed on male Wistar rats and male Sprague-Dawley rats. Histochemical, immunohistochemical and Western blot analysis were performed on m. tibialis anterior and m. masseter. Regeneration process of skeletal muscles was induced by injection of bupivacain. RESULTS AND CONCLUSIONS We have demonstrated that muscle regeneration caused a transient upregulation of MyoD and myogenin, but after reestablishment of normal muscle architecture there was no expression of MyoD and myogenin. Time course expression of MyoD and myogenin during regeneration in muscles of different developmental origin was similar. The main conclusion of our investigation is that the role of MyoD and myogenin is potentially as important in managing an adaptive and regenerative response of muscle fibers.

Fundamental medical sciences