The Role of the Na+/H+ Antiporter in Human Neutrophil NADPH-Oxidase Activation

The Na+/H+ antiporter has been shown to regulate activation of the human neutrophil. To delineate the role of the antiporter in the stimulation cascade, superoxide [O2-) generation was observed in PMA-stimulated neutrophils in which intracellular pH (pHi) was artificially manipulated by the use of nigericin, a K+/H+ ionophore, with and without use of the Na+/H+ antiporter inhibitor, dimethylamiloride (DA). Decreased O2- generation was observed in a Na+-free, 140 mM K+ buffer, but addition of nigericin restored this parameter of neutrophil activation to levels found in physiologic Na+ media. Further, the inhibitory effects of DA on O2- generation by cells incubated in a 10 mM Na+, 130 mM K+ buffer were totally reversed by a similar concentration of nigericin. O2- generated by a membrane preparation of the NADPH-oxidase, made from cells incubated under the same experimental conditions, paralleled whole cell studies, but the activity of the oxidase did not vary when suspended in the various reaction mixtures. These experiments support the role of the Na+/H+ antiporter in neutrophil activation as a metabolic regulator of pHi that influences receptor-coupled reactions proximal to expression of the NADPH-oxidase itself.