Hemoglobinemia in rats exposed to high altitude.

A hemoglobinemia occurred in rats exposed to a simulated altitude of 18,000 ft. No biochemical deficits in the erythrocytes or plasma were apparent, and the erythrocytic survival time was normal. This hypoxia-induced hemoglobinemia was not due to intravascular hemolysis and it coexisted with polycythemia, representing a unique hematologic condition. As a result of the hemoglobinemia in altitude-exposed rats, plasma haptoglobin was depleted, a 5- and 10-fold increase in the activities of heme oxygenase were induced in the liver and kidney, respectively, and there was a hemoglobinuria. The possible mechanism for the genesis of this hypoxia-induced hemoglobinemia is discussed.