Heme accumulation from exogenous sources and its effect on hemoglobin synthesis, iron metabolism, and maturation of Friend erythroleukemic cells is reported. Supplementation of culture medium with hemin (4 × 10-5 M) caused an increase in the cellular heme content by 210% and enhanced hemoglobin synthesis up to 190 μg/107 cells. (14C)-hemin added to the medium was detected in the de novo hemoglobin produced in the leukemic cells, and the amount of hemoglobin was proportional to the exogenous hemin concentration. Exogenous 5-amino levulinic acid was utilized for heme and porphyrin synthesis in induced and uninduced cells. (14C)-heme derived from (14C)-amino levulinic acid was extracted from hemoglobin and was dependent on the external 5-amino levulinic acid dose. The addition of 5-amino levulinic acid (5 × 10-4 M) increased hemoglobin synthesis to 130 μg/107 cells. The massive incorporation of exogenous 5-amino levulinic acid into heme occurred between the 1st and 4th days of differentiation, before initiation of endogenous heme synthesis from glycine after the 4th day of induction. (59Fe) accumulation in uninduced Friend cells was enhanced by exogenous hemin. The (59Fe) was incorporated into a femtin-like complex, with a PI range of 5.8-6.3. Friend cells induced with 2% dimethylsulfoxide accumulated and incorporated less (59Fe) in the presence of hemin. Unincorporated non-hemoglobin iron was found in a femtin-like complex. Dimethylsulphoxide (DMSO), protoporphyrin IX, izonicotinic acid hydrazide, and EDTA decreased iron accumulation and proportionally iron incorporation into heme. This decrease in iron incorporation due to these compounds was less pronounced compared with the hemin dependent inhibition. This may be partially due to the general toxicity of the combination of DMSO and hemin. Electron micrographs of cells after 5 days of differentiation showed a stimulating effect of hemin and 5-amino levulinic acid on cell maturation. The cells from hemin-enriched medium appeared to be polychromatophilic with nuclear condensation and an increase in hemoglobin content. Cells from the 5-amino levulinic acid-enriched medium were showed to be at a basophilic-like stage while dimethylsulfoxide-induced cells remained, from the morphological point of view, at the proerythro-blastic stage.
|Number of pages||9|
|State||Published - 1979|