Quantitative succinate dehydrogenase analysis in normal and ragged-red muscle fibers.

Single fiber analyses were performed in normal and diseased muscle by means of a high-resolution microphotometric method. We investigated the activity distribution of a mitochondrial marker enzyme, succinate dehydrogenase, within single muscle fibers. We differentiated between the central and the subsarcolemmal region. Both normal muscle fibers, and ragged-red fibers from patients with a mitochondrial myopathy showed significantly higher succinate dehydrogenase activities in the subsarcolemmal region. Since the fibers' supply of oxygen is accomplished by diffusion from capillaries located close to the sarcoplasmic membrane our results are of functional importance.