Connective Tissue and the Pentose Phosphate Pathway in Normal and Denervated Muscle

Abstract

DIRECT oxidation of glucose-6-phosphate through the pentose phosphate pathway is known to occur in various animal tissues. The enzymes glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), which are involved in the first two steps of this pathway, have been found in many organs. The activity of these enzymes in skeletal muscle is exceptionally low compared with that of most other mammalian tissues studied¹. Their activity does, however, increase in muscles undergoing atrophy. This increase appears to be relatively unspecific, as it has been observed in denervation atrophy, hereditary muscular dystrophy, muscle necrosis due to trauma or viral infection, and in myopathy induced by drugs^2–4. We have studied the G6PDH and 6PGDH activity in normal and denervated soleus and gastrocnemius muscles of the rabbit. Our findings suggest that the increase in activity of these enzymes may be the result, not of specific changes in the muscle cell itself, but rather a reflexion of the increase in connective tissue.