Comparison of erythropoietic response to erythropoietin-secreting stimuli in mice following polycythemia induced by transfusion or hypoxia.

The erythropoietic response, measured as RBC-59Fe uptake, in response to either 24-h exposure to hypoxia or administration of dexamethasone, isoproterenol, testosterone, or erythropoietin, was determined in both posthypoxic (PH) and hypertransfused (HT) polycythemic mice. Highly significant differences between PH and HT mice exposed to hypoxia or injected with dexamethasone, isoproterenol, or testosterone were observed, isotope incorporation being always higher in PH than in HT mice. On the other hand, the response to erythropoietin did not show a significant difference between PH and HT mice. These results suggest that PH mice have been preconditioned by exposure to hypoxia in a way that makes them more sensitive to at least some kinds of erythropoietic stimuli. Since these stimuli have been shown by others to increase erythropoietin production, the results support our hypothesis that hypoxia induces sensitization of the erythropoietin-producing organ(s).