Coexistence of fast and slow types of myosin light chains in a single fiber of rat soleus muscle.

Single muscle fibers were isolated from soleus and extensor digitorum longus muscle of adult rats. The muscle fiber type of single fibers was determined physiologically by the skinned fiber method according to the sensitivity to strontium (Sr) ions. The fiber type of single fibers was contrasted to the pattern of myosin light chains analyzed by one and two dimensional gel-electrophoreses. All the type 2 fibers isolated from soleus muscle contained both fast and slow types of myosin light chains.