Stimulation of Friend erythroleukemic cell cytodifferentiation by 5-amino levulinic acid; porphyrins, cell size, segregation of sialoglycoproteins, and nuclear translocation.

The late events of erythroid differentiation in Friend erythroleukemic cells (FELC), stimulated by 5-amino levulinic acid (5-ALA), were studied. Cultivation of the cells in 5-ALA-enriched media triggered a chain reaction, beginning with an immediate and rapid accumulation of endogenous porphyrins, in particular protoporphyrin and hemin. Incorporation of 14C-ALA was rapid and independent of dimethylsulfoxide (DMSO) induction. In parallel, on the second day of growth, a marked decrease in cell volume was elucidated by flow cytometry. The total protein content was reduced, while Fe uptake and hemoglobin synthesis were increased. The combination of DMSO and 5-ALA produced the most effective induction of the FELC, and the differentiation criteria were the most advanced. The cells exposed to the combined stimulation became loaded with heme and hemoglobin and their generation time was prolonged up to 35 h. Transmission electron microscopy of these treated cells showed a morphological alteration to pearlike cells, associated with a typical nuclear translocation phenomenon and a regional segregation of sialoglycoproteins. An uneven distribution of organelles was revealed; one part of the cell contained numerous ribosomes and the nucleus, while the other part was hemoglobinized, contained mitochondria, and the outer membrane was heavily labeled with ferritin hydrazide, a marker for sialoglycoproteins. The enhanced stimulation of Friend cells by 5-ALA promoted an advanced step of erythroid maturation that has much in common with the late events of normal nuclear extrusion process.