Enzyme activity patterns of myosin ATPase, alpha-glycerophosphate dehydrogenase and succinate dehydrogenase within different muscle fibre types.

Muscle fibre compositions of five different rabbit muscles were determined by combining two enzyme-histochemical reactions (NADH tetracolium oxidoreductase and myosin ATPase after alkaline preincubation). The differentiation into the fibre types, fast twitch glycolytic (FTG), fast twitch oxidative (FTO), and slow twitch oxidative (STO) was possible by a reliable staining classification. Aim of the study was the estimation of enzyme activity patterns within the three different fibre types. For this purpose, four serial cross-sections with several enzyme histochemical reactions were performed: alkaline combination method for fibre type determination, the reactions of myosin ATPase, alpha-glycerophosphate dehydrogenase (GPDH), and succinate dehydrogenase (SDH). The measurement procedure for the estimation of enzyme activities was based on the proportionality between the intensity of the enzyme histochemical staining reaction and the degree of enzyme activity. The activities of GPDH (indicator for glycolytic metabolism) and SDH (oxidative metabolism) were inverse. The calcium-activated myosin ATPase showed only little activity in slow twitch fibres after alkaline preincubation. In contrast to slow twitch fibres, ATPase activity in fast twitch fibres was relatively high. The results showed that the classification of muscle fibre types due to their myosin ATPase activities and their main metabolisms (oxidative and glycolytic respectively) is justified.