The local anaesthetic (Bupivacaine (1-n-butyl-DL-piperidine-2-carboxylic acid-2, 6-dimethyl anilide hydrochloride) has been used to induce myofiber damage (and thus satellite cells proliferation) and thereby represents a tool for increasing the yield of myoblasts from adult muscles. Replicating satellite cells were isolated by enzymatic dissociation from soleus (slow type) and tibialis anterior (fast type) muscles of adult rats, and categorized by the isoform (embryonic, fast and slow) of myosin heavy chain (MHC) expressed following myotube formation in a similar in vitro environment. According to light microscopic criteria, no morphological differences exist between the satellite cell cultures obtained from adult fast and slow muscles after Bupivacaine injection. On the other hand the derived myotubes express, beside the embryonic type, the peculiar myosin heavy chains which characterize the myosin pattern of the donor muscles.