Biosynthesis of ferritin subunits from different cell lines of HL‐60 human promyelocytic leukaemia cells and the release of acidic isoferritin‐inhibitory activity against normal granulocyte‐macrophage progenitor cells

Biosynthesis of acidic isoferritins was investigated in human promyelocytic HL‐60 cells, characterized by diploid (2C), tetraploid (4C) and mixed diploid–tetraploid (2C–4C) DNA cell lines. The three cell lines were studied for the biosynthesis of ferritin and its subunits and for the release of acidic isoferritin‐inhibitory activity against normal CFU‐GM before and after addition of DMSO. While the tetraploid and mixed diploid–tetraploid cell lines synthesized more H‐ (M_r= 21) than L‐subunits (M_r= 19) after induction, the tetraploid line synthesized more H‐subunit before and after induction, compared to the diploid line. The release of acidic isoferritin‐inhibitory activity was greater before than after induction in both cell lines, but the tetraploid cell line released more acidic isoferritin‐inhibitory activity consistent with its greater production of M_r= 21 subunit. However, after induction no inhibitory activity could be detected from the diploid cells and much less activity was detected with the tetraploid cells, suggesting that differentiation caused a decrease in production of acidic isoferritin‐inhibitory activity.