The relationships between plasma Epo and the relevant factors in rats. Hb in peripheral blood (A), plasma iron (B), plasma ferritin (C), and iron concentration in the kidney (D). The rats were injected with E₂ at 1 mg/kg 3 times a week for 2 months and fed the Basal Diet 5755 (solid circles, n = 16) or the Low-Iron Purified Diet (open circles, n = 17).