Immunocytochemical studies of cytochrome oxidase subunits in skeletal muscle of patients with partial cytochrome oxidase deficiencies.

Muscle biopsies from 17 patients with partial cytochrome oxidase deficiencies were investigated using immunocytochemical techniques for the localisation of cytochrome oxidase subunits. Antisera to subunits II/III (mitochondrially coded) and subunits IV, Vab, VIbc, VIIa, VIIbc and VIII (nuclear coded) showed clear particulate immunoreactivity in the muscle fibres of normal control biopsies. In the patients studied, muscle fibres with absent or decreased cytochrome oxidase activity also showed decreased immunoreactivity affecting all enzyme subunits. Particularly close correlation was seen between percentages of fibres showing absent enzyme activity and those showing decreased immunoreactivity for subunits II/III which are catalytic in function. The regulatory subunits IV-VIII were affected to varying degrees with different patterns of subunit loss occurring in individual muscle fibres.