Properties of mitochondria from hearts of cattle acclimatized to high altitude

Abstract

Hearts of domestic cattle from two groups, one born and raised at sea level and the other born and raised at an altitude of 4250 m, were studied to determine whether any mitochondrial adaptations to high altitude could be demonstrated. Direct counts of mitochondrial number revealed a 40 % increase in the high altitude hearts, but mitochondrial size was the same as at sea level. Measurements of enzyme content indicated an individual mitochondrial increase in electron transport system; and oxygen uptake and cytochrome a oxidase, per mitochondrion, were increased in the same proportion. These changes are discussed as an intracellular mechanism which would serve to preserve oxidative metabolism in hypoxia, particularly under exercising conditions. The effective conservation of oxygen pressure head by this means is probably less than one mm Hg.