Phorbol esters and chemotactic factor induce distinct changes in cytoplasmic Ca2+ and pH in granulocytic like HL60...

Differentiation of HL60 cells into neutrophil-like cells after exposure to dimethylsulfoxide is accompanied by an increase in intracellular pH (pHi) which results from an increased activity of the Na+/H+ antiporter at physiological pHi value, but not at acidic pHi values. The functional responses of differentiated HL60 cells to the chemotactic peptide, N-formylmethionylleucylphenylalanine (fMLP), and to phorbol myristate acetate (PMA) were studied. In differentiated cells fMLP produced a large increase in cytosolic Ca2+ levels and a small biphasic change in pHi, whereas PMA produced cellular acidification, which was potentiated by ethylisopropylamiloride and no change in [Ca2+]i. In undifferentiated HL60 cells, PMA produced the opposite effect on pHi, i.e., a cellular alkalinization. The extent of the acidification produced by PMA in differentiated HL60 cells correlated with the production of reactive oxygen species.