Minimal utilizable oxygen and the oxygen dissociation curve of blood of rodents.

Abstract

Measurements of dissociation curves were made in 18 rodent species. The minimal level at which utilizable oxygen can be removed from the envrionment was also determined. This is designated as the "critical oxygen tension. " There is a correlation between the ability of certain animals to extract oxygen from the environment to a minimal tension and the position of their blood oxygen dissociation. Smaller rodents cannot remove oxygen from their environments to as low a level as can larger rodents. Smaller rodents have a higher hemoglobin-oxygen loading tension and larger rodents have a comparatively lower hemoglobin-oxygen loading tension. There also appears to be a correlation of these factors with habits and habitats of several species which overrides the factor of size. Rodents which normally live at high altitudes or in burrows where ambient oxygen tensions may become low have a lower hemoglobin-oxygen loading tension than do their sea-level relatives which may be larger in size and, also, they can extract oxygen from their surroundings to a lower partial pressure.