Impairment of Na+/H+ exchange underlies inhibitory effects of Na+‐free media on leukocyte function

摘要

>Inhibition of activation has been reported when neutrophils are suspended in Na+-free media. We considered the possibility that impairment of cellular pH (pH_i) regulation due to elimination of Na+/H+ exchange underlies this effect. In the absence of Na+, the phorbol ester-induced respiratory burst was partially inhibited and a concomitant cytoplasmic acidification recorded. Using nigericin/K+ to clamp pH_i we demonstrated that the acidification accounts for the inhibition of O₂ uptake. Moreover, in Na+-free media, relieving the acidification by means of ionophores restored maximal O₂ consumption. It was concluded that Na+ is not directly involved in signal transduction during stimulation. Instead, omission of Na+ affects neutrophile activation indirectly, by impairing pH_i regulation.