Release of cytochromes from hypoxic and reoxygenated guinea pig heart

Isolated, perfused hearts from guinea pigs were subjected to hypoxia for 30 minutes followed by reoxygenation for 30 minutes. Cellular damage was assessed by measuring the release of the cytoplasmic enzyme lactate dehydrogenase and the mitochondrial markers cytochrome c and cytochrome oxidase. The release of the enzymes was correlated with electron microscopy. Hypoxia induced an increase in the release of lactate dehydrogenase and cytochrome c. During reoxygenation, the release of lactate dehydrogenase was exacerbated while that of cytochrome c decreased, suggesting a partial recovery of the mitochondria. Cytochrome oxidase was not detectable in the extracellular space during hypoxia or reoxygenation. It is suggested that cytochrome c is a specific marker for damage to mitochondria caused by hypoxia and its loss may affect respiratory chain function.