SUCCINIC DEHYDROGENASE IN PIGEON PECTORALIS DURING DISUSE ATROPHY.

Abstract

Quantitative and histochemical changes in succinic dehydrogenase activity in pigeon breast muscle was studied during one to sixty days of disuse after immobilization of the wings. Muscle enzyme activity was found to decrease from the first day, reaching its lowest level after seven days. Histochemical observations on red and white muscle fibers showed that after seven days atrophy, the majority of red fibers had lower enzyme activity; a few others showed higher activity. In white fibers on the other hand, a uniform increase over normal in enzyme activity and mitochondrial number was seen. These changes in the two types of fibers were less conspicuous during the later stages of atrophy. Thus the general level of oxidative metabolism in muscle as a whole was lowered in spite of the slight increase in level of SDH in white fibers. It is suggested that in both red and white fibers there was a shift, of aerobic to anaerobic metabolism, or vice versa.