Further evidence for behaviorly induced hypoxic conditions in subordinate mice.

When two male mice fight to establish social rank, the subordinate exhibits marked splenomegaly, reticulocytosis and decreased hematocrit. Individuals were isolated at weaning, paired 3 weeks later for two 30-min encounter periods daily for up to 3 weeks. After 2 days and 1 week encounter periods, subordinates had significantly decreased levels of hemoglobin in the kidney compared to dominants and controls. Subordinates had increased ATP levels in blood after 1, 2 and 3 weeks of encounter, bone marrow erythroid hyperplasia, as well as a substantial increase in the erythropoietin titre and Fe99 incorporation in spleen and blood.