Effects of anabolic androgenic steroids on regenerating skeletal muscles in the rat

We have examined the effect of male sexual hormones on the regeneration of skeletal muscles. Degeneration/regeneration of the left soleus and extensor digitorum longus muscles (EDL) of Wistar male rats was induced by an injec tion of snake venom (2 mu g. Notechis scutatus scutatus). During the muscle regeneration (25 days), rats were treated with either oil (CON), nandrolon e (NAN). NAN combined with exercise (NAN + EXE) or were castrated (CAS). Mu scle growth and myosin heavy chain (MyHC) isoform content of regenerating m uscles were studied. Castration altered the concentrations of MyHC in venom -treated EDL (P < 0.01) and soleus (P < 0.05). NAN increased the mass (P < 0.01) of regenerating soleus and decreased the relative amount of fast MyHC protein (% of total. P < 0.05). The effect of NAN + EXE on the fast MyHC p roteins of venom-treated soleus was opposite (P < 0.05). NAN and NAN + EXE were without effect on the regenerating EDL (P > 0.05). In conclusion, it i s possible that male sexual hormones play a role in the growth (synthesis o f contractile proteins) of regenerating muscles in rat. In addition, contra ry to NAN + EXE, NAN could be beneficial to soleus regeneration.