Hemopoietic stress and fetal hemoglobin synthesis: comparative studies in vivo and in vitro.

Baboons exposed to acute hemolytic stres increase their production of fetal hemoglobin (HbF). Although the maximal in vivo HbF levels attained in 5 treated animals varied from 6.4% to 34.8%, their cultured bone marrow erythroid cells reverted to the fetal pattern of hemoglobin synthesis. These data suggest that HbF synthesis is modulated by the interaction of inhibiting and promoting factors, which is different among animals in vivo but equal in the cultures of their bone marrow erythroid cells.