In order to ascertain whether recombinant human erythropoietin (EPO) therapy would result in further intestinal iron absorption in the setting of systemic iron loading, iron absorption was measured in iron-loaded rats receiving EPO therapy and a control group of iron-loaded rats. Parenteral iron dextran (100 mg) resulted in hepatic siderosis with predominantly a reticuloendothelial distribution. EPO was given by intraperitoneal injection (100 U/kg) for 10 days. Radioiron absorption was measured by total body counting. Iron absorption in EPO-treated rats was 4.8 +/- 2.0% (n = 12) and 4.5 +/- 2.2% (n = 10) in the control rats (p greater than 0.05). Mean hemoglobin in the EPO rats was 201 +/- 12.5 g/L and 140 +/- 18.2 g/L in the control rats (p less than 0.001). Mean hepatic iron concentration was 73 +/- 16 mumol/g in the control rats and 34 +/- 9.1 mumol/g in the EPO-treated rats (p less than 0.001). This study suggests that iron-loaded rats do not demonstrate an increase in intestinal iron absorption with EPO therapy despite a significant erythropoiesis. The reduction in hepatic iron concentration suggests that reticuloendothelial iron is accessible and mobilized to produce new red blood cells.