Effect of Hypoxia and Hypercapnia Alone and in Combination upon the Circulating Red Cell Volume of Rats 1

Abstract

Summary

Three groups of 50 rats each were exposed for periods of up to 24 days to either hypoxia (70 Torr PI_O2 ), hypercapnia (140 Torr PI_O2 , 60 Torr PI_CO2 ), or a combination of this level of hypoxia and hypercapnia.

The combined condition resulted in a much smaller rise in circulating red cell volume per body weight than in rats exposed to hypoxia alone. The increase that did occur could be mainly attributed to a release of stored red cells into the circulation. During hypercapnia, plasma volume increased with only small changes in numbers of circulating red cells. This resulted in a depression of hematocrit.

It is still not clear whether concomitant hypercapnia increased oxygen levels in the hypoxic-hypercapnic rats sufficiently to remove the erythropoietic stimulus, or if CO₂ actually inhibited erythropoiesis.