Metabolic performance during hypoxia in native and acclimated pocket gophers

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Abstract
To evaluate the adaptive significance of hematological and morphological changes following exposure to hypoxia, oxygen consumption (.ovrhdot.VO2) was measured in pocket gophers (Thomomys bottae and T. umbrinus melanotis) during combined cold and hypoxic stress. Animals examined included gophers native to sea level (265 m) or high altitude (3200 m), sea level gophers acclimated for 3 mo. to simulated altitude (3400 m), and sea level animals kept as captive controls for 3 mo. Based on analysis of critical oxygen tension (Pc) and the rates of decline in .ovrhdot.VO2 below Pc (.alpha.), pocket gophers native or acclimated to high altitude showed significantly greater hypoxic tolerance than sea level natives and controls. The blood oxygen capacity of high-altitude-acclimated gophers was 15-20% higher than in all other groups, while 2,3-diphosphoglycerate concentration was similar in all groups. Skeletal muscle myoglobin concentration increased 16% in high-altitude-acclimated animals compared to controls. The alveolar fraction and specific alveolar surface area in lungs of high-altitude native and acclimated gophers were greater than those of sea-level natives and controls. Although these results show that improvements in hypoxic tolerance can develop under environmental influence, the mechanisms of adaptation at the blood and tissue level apparently are different between high-altitude natives and hypoxia-acclimated animals.