HEME IS NECESSARY FOR A CONTINUED INCREASE IN FERROCHELATASE MESSENGER-RNA IN MURINE ERYTHROLEUKEMIA-CELLS DURING ERYTHROID-DIFFERENTIATION

The level of mRNA encoding ferrochelatase (FeC) was examined in two mu rine erythroleukaemia (MEL) clones, DS and DR, a DMSO-sensitive, and a DMSO-resistant clone, respectively. DS cells undergo erythroid differ entiation by DMSO treatment with a marked increase in haem synthesis, while DR cells fail to do so due to the lack of the erythroid-specific delta-aminolaevulinate synthase (ALAS-E). Both DS and DR cells showed an increase in the level of FeC mRNA within 18 h of DMSO treatment. T he level of FeC mRNA in DR cells was then decreased, while that in DS cells continued to increase for 72 h. Treatment with haemin significan tly increased FeC mRNA in DR cells. When cells were treated with both DMSO and haemin, the level of FeC mRNA in DR cells increased to a leve l comparable to that in DS cells. These findings suggest that the fail ure to maintain increased FeC mRNA DR cells after DMSO treatment may b e due to a deficiency of haem in these cells.