EVALUATION OF PATIENTS WITH LACTIC-ACIDOSIS USING MICROPHOTOMETRIC MITOCHONDRIAL ENZYME ASSAY IN SINGLE MUSCLE-FIBERS

Microphotometric enzyme assay in single muscle fibers was performed on two patients with lactic acidosis. Neither case showed ragged red fib ers upon histochemical evaluation. Biochemical analysis of mitochondri al enzymes demonstrated low normal cytochrome c oxidase (COX) activity in Case 1 and deficient COX in Case 2. Quantitative single muscle fib er analysis in patients showed marked variation in COX activity in Cas e 1, reflecting mosaic distribution of fibers with near-normal COX act ivity and with defective COX activity. These data suggest that this mi crophotometric assay may be valuable for elucidating the significance of 'partial enzyme deficiency'. In addition, this assay method may be applied to needle biopsy specimens.