Evidence against a requirement for Na /H exchange activity for proliferation or differentiation of HL60 leukemic cells.

Abstract

Although increased Na+/H+ exchange (antiport) activity has been shown to precede both granulocytic and monocytic differentiation of HL60 cells, its requirement for this process remains controversial. We show here that, in the absence of HCO3-, the Na+/H+ exchanger is the predominant mechanism involved in rapid recovery of pHi from cytoplasmic acidosis; however, in the presence of HCO3-, other mechanisms also contribute to pHi homeostasis. In the absence of HCO3-, dimethyl sulfoxide and 4 beta-phorbol 12-myristate 13 alpha-acetate result in an acute activation of antiport activity, whereas all-trans-retinoic acid, 1,25-dihydroxyvitamin D3, gamma-interferon, and tumor necrosis factor alpha do ..