Focal deficiency of cytochrome c oxidase and of mitochondrial ATPase with histochemical evidence of loosely coupled oxidative phosphorylation in a mitochondrial myopathy of a patient with bilateral ptosis. An enzyme histochemical, immunocytochemical and fine structural study.
In the skeletal muscle of a patient with bilateral ptosis suggestive of progressive external ophthalmoplegia (PEO), but without ragged red fibres, electron microscopy revealed a moderate proliferation of mitochondria in nearly all fibres. A focal absence of cytochrome c oxidase and of mitochondrial ATPase was demonstrated histochemically in 3.2% and 1.4% respectively of the fibres. In 0.9% of the fibres both enzymes were deficient. In addition, mitochondrial ATPase, the ATP-synthesizing enzyme latent in controls, showed activation already before addition of an uncoupler. This indicates loosely coupled oxidative phosphorylation. The findings point to a complex derangement of mitochondrial function. Immunocytochemistry of cytochrome c oxidase favours the assumption that the defect is based on a highly diminished content of immunoreactive enzyme protein.
Müller-Höcker
J
J
Stünkel
S
S
Pongratz
D
D
Hübner
G
G
D000251:Adenosine Triphosphatases / Q000172:deficiency* / Q000378:metabolism; D001763:Blepharoptosis / Q000201:enzymology* / Q000473:pathology; D002648:Child; D030401:Cytochrome-c Oxidase Deficiency; D004789:Enzyme Activation; D006651:Histocytochemistry; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology* / Q000648:ultrastructure; D010085:Oxidative Phosphorylation
D000251:Adenosine Triphosphatases