Respiratory chain defects in the mitochondria of cultured skin fibroblasts from three patients with lacticacidemia.

The cultured skin fibroblasts from three patients with lacticacidemia were found to have low rates of 1-[14C]pyruvate oxidation in the face of normal pyruvate dehydrogenase activity. After incubation with 1 mM glucose, these three cell strains also exhibited lactate/pyruvate ratios which were three times greater than those of controls. In two of the patients, both ATP and oxygen consumption in fibroblast mitochondrial preparations was deficient with NAD-linked substrates but normal with succinate and ascorbate/N'N'N'N' tetramethyl phenylene diamine. In the third patient, ATP synthesis in mitochondrial preparations was deficient with all substrates tested. Measurement of Rotenone-sensitive NADH-cytochrome c reductase in mitochondrial preparations from skin fibroblasts showed that two of the patients had 14 and 18%, respectively, of control activity. In the third patient, cytochrome oxidase activity was 15% of that in controls. We conclude that respiratory chain defects can be demonstrated in cultured skin fibroblasts with consistency using a number of different techniques.