Enzyme histochemical alterations in human skeletal muscles after tenotomy and after spontaneous rupture of the tendon.

The authors studied the histochemical alterations of human skeletal muscles after tenotomy and after spontaneous rupture of the tendon. Both succinate dehydrogenase (in type I fibers), and myofibrillar ATP-ase (in type 2 fibers) activity was decreased in all injured muscles. In the intact antagonists and contralateral muscles alterations were not found. The creatine phosphokinase and aldolase activity were decreased also in injured muscles. The lactate dehydrogenase activity was various both in affected and in unaffected muscles. Two weeks or more after the injury of the tendon in injured muscles the number of type 1 fibers were decreased and therefore a mathematically significant type 2 fibre predominance occurred. Atrophy involve both type 1 and type 2 fibers, but type 1 fibre atrophy was more pronunced as type 2 fibre atrophy.