Histochemical classification of myofiber types in the triceps surae and flexor digitorum superficialis muscle of Japanese macaques.

Abstract

Leg muscles of Japanese macaques (Macaca fuscata) were examined to characterize histochemical properties of myofiber types. Myofiber types were classified by differences in reactivity for myosin ATPase, NADH tetrazolium reductase (NADH-TR), and menadione-linked glycerol-3-phosphate dehydrogenase (3-GPD). The myofibers that reacted strongly for acid-stable myosin ATPase and were weakly reactive or unreactive for alkali-stable myosin ATPase were classified as slow-twitch/oxidative (SO) myofibers, which reacted strongly for NADH-TR and weakly to moderately for 3-GPD. The myofibers that were unreactive to moderately reactive for acid-stable myosin ATPase and strongly reactive for alkali-stable myosin ATPase were classified into fast-twitch/oxidative/glycolytic (FOG) myofibers with a moderate to strong activity for NADH-TR and 3-GPD and into fast-twitch/glycolytic (FG) myofibers with a weak NADH-TR activity and a strong 3-GPD activity. Slow-twitch myofibers with a strong activity for NADH-TR and 3-GPD were characterized as slow-twitch/oxidative/glycolytic (SOG) myofibers. The presence or absence of the SOG myofibers depended on the individuals. The soleus muscle had larger percentages of SO myofibers than of FOG and FG myofibers. The gastrocnemius and flexor digitorum superficialis muscles generally had larger percentages of FG myofibers than of FOG and SO myofibers including SOG myofibers.