Abstract

AIMS:

To evaluate the mitochondrial respiratory enzyme activities in blood cells of Leber's hereditary optic neuropathy (LHON) with 11778 point mutation of mitochondrial DNA.

METHODS:

Assays for the activities of NADH-cytochrome c reductase (complex I+complex III), succinate-cytochrome c reductase (complex II+complex III), and cytochrome c oxidase (complex IV) on blood cell mitochondria of seven LHON patients and 15 normal controls.

RESULTS:

There was no statistically significant difference in NADH-cytochrome c reductase and cytochrome c oxidase activities between LHON patients and controls, but activities of succinate-cytochrome c reductase in LHON patients was significantly elevated compared with normal controls.

CONCLUSION:

The observations that the activity of NADH-cytochrome c reductase is normal but that of succinate-cytochrome c reductase is increased in LHON patients with 11778 point mutation of mitochondrial DNA indicate an elevation of complex II activity, which may be due to a nuclear compensatory effect for defects of the respiratory function of mitochondria.