Dose-response effects of 5-azacytidine on hemoglobin production. (A) Ion exchange HPLC tracings of hemolysates from cells at the completion of the in vitro differentiation procedure. Fetal (F) and adult (A) hemoglobin peaks are indicated. (B) Summary of Hb HPLC data showing a reciprocal effect of 5-azacytidine on fetal and adult hemoglobin levels.