In vivo control of mitochondrial enzyme concentrations and activity by oxygen

Abstract

Newborn and adult dog heart mitochondria were prepared from animals chronically adjusted to varying arterial oxygen tensions. Similarly, rat liver and heart mitochondria were isolated from animals acutely exposed to lowered inspired O2. After isolation, all mitochondrial samples were assayed under normoxic conditions. Respiratory activity in State 3 or in the uncoupled state, increased after hypoxia and decreased after increased in vivo oxygenation. The turnover of cytochrome oxidase increased in hypoxia and decreased after increased oxygenation. After chronic hypoxia cytochrome oxidase, cytochrome c and b concentrations decreased per mg of mitochondrial protein. All mitochondrial preparations were well coupled and exhibited normal capabilities to perform oxidative phosphorylation. The data are interpreted to indicate sensitive control of mitochondrial respiratory capacities by O2 in vivo.