ENZYMATIC-ACTIVITY AND MORPHOLOGICAL-DIFFERENTIATION IN DE-NOVO INNERVATED HUMAN MUSCLE CULTURES

In the present series of experiments, we studied the effects of develo pmental neural control on morphological differentiation and on the act ivity of muscle-specific (creatine kinase, CK; phosphoglycerate mutase , PGAM; phosphorylase, PPL; and phosphofructokinase, PFK) and non-spec ific (acid maltase, AM; glucose-6-phosphate dehydrogenase, G6PD), huma n muscle enzymes in de novo innervated muscle cultures. Following inne rvation of muscle cultures, we noted an increase in the activity of CK , PPL, PFK and AM along with a reduction in G6PD activity. There was a lso a change of the CK isoenzymes present in the myotubes, i.e. BB and MB are the major isoenzymes in non innervated cultures, but MM become s predominant following innervation. In the case of PGAM, the only iso enzyme present in the non innervated cultures was BB while the MM isof orm appeared only after a prolonged innervation period in most cases - with the exception of AM - these changes in enzyme activity and in th e type of isoenzymes present, demonstrate that innervated cultures are more similar to mature muscle. This maturation of enzymatic activity correlates well with the morphological maturation of the myotubes obse rved following innervation. Such innervated cultures therefore represe nt a better model with which to study the morphological and biochemica l abnormalities associated with neuromuscular diseases.