Freeze fracture analysis of muscle plasma membrane in bupivacaine HCl-induced degeneration and regeneration.

We did freeze fracture analysis of bupivacaine HCl-induced muscle fiber damage. The muscle plasma membrane in rat extensor digitorum longus and soleus muscle was analyzed for the density of orthogonal arrays and caveolae at periods of five minutes to 60 days after application of the myotoxin. In degenerating muscle a decrease in the density of caveolae was observed. In regenerating extensor digitorum longus muscle, a decrease in the density of orthogonal arrays and an increase in the density of caveolae was present. The results show that freeze fracture alterations in fast twitch regenerating muscle are similar to those seen in the muscles of patients with Duchenne muscular dystrophy.