HEMOGLOBIN SWITCHING IN SHEEP - A COMPARISON OF THE ERYTHROPOIETIN-INDUCED SWITCH TO HBC AND THE FETAL TO ADULT HEMOGLOBIN SWITCH

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 56  (3) , 488-494
Abstract
Stimulation of sheep erythropoietic progenitor cells by erythropoietin (epo) was studied with regard to its effect on the pattern of Hb production. An analysis of Hb synthesis in BFU-E [erythropoietic burst-forming units]- and CFU-E [erythroid colony-forming units]-derived colonies from fetuses homozygous for HbA (AA) (homozygous also for the .beta.c gene responsible for HbC production) or HbB (BB) (lacking the .beta.c gene) indicated the following. Colonies derived from precursor cells from 51 and 89 day fetuses exhibited small but detectable increments of HbB synthesis with prolonged incubation in vitro. This response was not dependent on the epo concentration. Erythropoietic precursor cells from a 124 day BB fetus were already committed to HbB synthesis, since HbF production was replaced by HbB on successive days in vitro as erythroid colonies matured; this switch was not affected by varying the epo concentration. Progenitor cells from a 124 day AA fetus responded to higher doses of epo by forming colonies in which more HbC was made at the expense of HbF and HbA. Erythropoietic stress did not result in induction of HbF in vivo or in erythroid colonies derived from CFU-E in young adult BB sheep, whereas prior studies showed induction of HbC synthesis under analogous conditions in colonies derived from young adult AA sheep. The epo-induced HbF (or HbA) to HbC switch and the fetal to adult Hb switch are regulated by different mechanisms.