Compared effects of irradiation and cyclophosphamide induced erythroid aplasia on the catabolism of exogenous erythropoietin.

The effect of erythroid aplasia on the clearance rate of exogenous erythropoietin from the circulation has been studied in irradiated (200, 400 and 800 r) and cyclophosphamide (50 mg/kg) treated rats. After irradiation, the T1/2 was increased from 1.5 h in controls to 2.3 h. In spite of similar aplasia, the T1/2 observed after cyclophosphamide administration was identical to the T1/2 in controls. These results suggest that the action of X-rays on the catabolism of erythropoietin is independent of erythroid aplasia and could be related to an extramedullary effect of irradiation.