Connective tissue metabolism in normal and atrophic skeletal muscle

The first two enzymes of the pentose-phosphate pathway (G6PD and 6PGD) were studied in rabbit skeletal muscle. Their activities closely paralleled the connective tissue levels in each individual muscle, and they increased in atrophying muscles at the same rate as connective tissue. Skeletal muscle tendons and subcutaneously implanted polyvinyl sponges, both of which consist of relatively pure connective tissue, displayed much higher activity of these enzymes than the muscle homogenates. These results suggest that pentose synthesis in muscle is mostly confined to its connective tissue elements, raising the possibility of a role for connective tissue in the biosynthetic processes of skeletal muscle. The contribution of connective tissue to the results of muscle quantitative studies may be significant, and even overshadow other values in atrophic muscles, where the muscle cell population may be greatly reduced. The interpretation of quantitative biochemical studies on pathological muscle samples should take this factor into consideration.