Quantitative cytochemistry of succinic dehydrogenase activity in rat mitochondria.

OBJECTIVE To set up a computer-assisted morphometric procedure to cytochemically measure the activity of succinic dehydrogenase (SDH). STUDY DESIGN In rat mitochondria from Purkinje cell perikarya and frozen muscle samples, SDH activity was selectively evidenced by the copper ferrocyanide method. On the SDH-positive organelles we measured the following parameters: number of mitochondria per cubic micrometer (numeric density [Nv]), volume fraction of organelles per cubic micrometer (volume density [Vv]), average mitochondrial volume (V) and intramitochondrial area density of the SDH reaction (area of the precipitates/total mitochondrial area [R]). RESULTS In both fresh Purkinje cells and frozen muscle cells the positive organelles were sharply evident. By considering Vv, Nv and V altogether in a given experimental group, a reliable evaluation of the morphologic rearrangements of the cellular metabolic hardware can be obtained. Measurements of R provides information on the functional efficiency of each organelle. CONCLUSION Quantitation of SDH-positive mitochondria is closely associated with the amount of enzyme molecules present and active within the organelles. Thus, quantitative assessment of the copper ferrocyanide reaction contributes to the evaluation of mitochondrial metabolic competence.