Stimulation of fetal hemoglobin synthesis in baboons by hemolysis and hypoxia.

Abstract

Fetal Hb (HbF) levels in the peripheral blood of baboons (Papio cynocephalus) increased from an average value of 0.78% to 18.1% during the recovery phase from phenylhydrazine-induced hemolytic anemia. A similar increase was observed in animals exposed to hypobaric hypoxia. Large individual variations in the maximal HbF levels were observed which could not be correlated with the ages of the animals. Reinduction of hemolysis in 2 fully recovered animals resulted in HbF levels that were of similar magnitude as in the preceding episode, suggesting the possibility of genetically determined individual variations in the rate of HbF synthesis under the same conditions of erythropoietic stimulation. Reticulocytes from the animals subjected to hemolysis or hypobaric hypoxia synthesized similar absolute quantities of HbF in vitro. The physiological switch from the synthesis of HbF to that of adult Hb during ontogeny can apparently be reversed in adult nonhuman primates by conditions of erythropoietic stress known to be associated with high erythropoietin levels. These findings open the possibility that HbF synthesis in adult humans may be therapeutically modulated in individuals who might benefit from increased levels of HbF, such as patients with sickle cell anemia.