Oxidative phosphorylation during altitude acclimation in rats

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Abstract
Oxidative phosphorylation was studied in liver mitochondrial preparations from rats continuously exposed to 25,000 ft. altitude for 1-3 days. After 1 day the ADP [adenosine diphosphate]: O ratio was lowered with either succinate or glutamate as substrate, Mg++-stimulated ATPase activity was increased by 33%, and succinate respiration was increased and could not be reduced with oligomycin. These data suggested that hepatic mitochondria were partially uncoupled during the 1st day of exposure. However, uncoupling was not extensive enough to alter irreversibly the functional integrity of the mitochondria. This was shown by the finding that deterioration of hypoxia-altered mitochondria was not accelerated during in vitro incubation. Mitochondria isolated from rats exposed for 3 days exhibited none of the above properties, indicating they were no longer uncoupled. However, respiratory control values and DNP-activated ATPase activity were depressed, suggesting that the phosphorylation reactions were impaired. Alterations which occurred in mitochondria during 1-3 days of exposure appeared to depend on the state of acclimation of the animal (as judged by serum enzyme, hematocrit, and histopathologic changes).