Activation of the superoxide-generating NADPH oxidase by phorbol ester or zymosan induced a cytoplasmic acidification when liver macrophages were incubated in sodium free media or in the presence of amiloride. Staurosporine or desensitization of protein kinase C inhibited phorbol ester-and zymosan-induced pH changes and generation of superoxide. The intracellular pH remained unchanged in cells incubated in physiological sodium media. Ionomycin and arachidonic acid did not induce a change in intracellular pH or a generation of superoxide. Fluoride, which has been shown to induce a translocation of protein kinase C in these cells, did not elicit superoxide generation but induced a decrease in intracellular pH. These experiments support (1) a role of the Na+/H+ antiporter in macrophages as a metabolic regulator of intracellular pH upon stimulation of the superoxide-generating NADPH oxidase, and (2) suggest an involvement of protein kinase C in this process.
