Do enzyme activities vary along muscle fibres?

Distribution of succinate dehydrogenase activity along muscle fibres has been studied qualitatively by histochemistry on single micro-dissected rat muscle fibres and quantitatively by comparative kinetic microphotometry on longitudinal muscle sections. Qualitative staining reactions showed no appreciable variations in enzyme activity along the fibres regardless of fibre type. By quantitative assessment, minor variations were found along fibres but were within the range of the experimental error. These variations are of the same magnitude as those observed in enzyme activities of pieces of the same fibre by means of quantitative microchemical methods, performed in our laboratory (Spamer and Pette 1979; Nemeth et al. 1980a, b). Our results provide evidence that the enzyme levels are the same along the course of a muscle fibre.