Decreased activities in mitochondrial inner membrane electron transport system in muscle from patients with Kearns-Sayre syndrome.

The present study shows biochemical data on skeletal muscle from 5 patients with Kearns-Sayre syndrome (KSS). Enzyme activities per muscle wet weight in the electron transport system of inner mitochondrial membrane were not significantly different in KSS from those in normal subjects except one patient with long duration of symptoms. On the other hand, mitochondrial contents were increased and enzyme activities per mitochondrial protein in the electron transport system were markedly decreased in the muscle of all cases. These results suggest that the decreased enzyme activity of the mitochondrial electron transport system in each mitochondrion may result in a compensatory increase in mitochondrial contents in the muscle of KSS.