Keshan disease--an endemic mitochondrial cardiomyopathy in China.
Keshan disease (KD) is a cardiomyopathy endemic in certain areas of China, characterized by severe deterioration and multiple focal necrosis. In the present paper we describe abnormalities of the structure and function of myocardial mitochondria from patients with subacute Keshan disease. Activities of succinate dehydrogenase, succinic oxidase, cytochrome c oxidase, H(+)-ATPase and its sensitivity to oligomycin and the response of membrane potential to energization by ATP were significantly decreased. However, the spectrum of reduced-minus-oxidized cytochromes in patients' mitochondria showed no obvious difference in the content of cytochrome c oxidase (aa3). There was also a marked decrease in lipid fluidity of affected mitochondria, and an abnormal amount of moderately electron dense amorphous inclusions. Electron-microscopic x-ray microanalysis and exposure to protein digestion reagent demonstrated that these inclusions are not Ca3(PO4)2, but are, probably, proteinaceous in nature. Affected mitochondria had markedly decreased selenium content. The defects in myocardial mitochondria from patients with chronic Keshan disease were less extensive than those in patients with subacute Keshan disease. We propose that Keshan disease be classified as a form of "mitochondrial cardiomyopathy".