title: Impairment of Na+/H+ exchange underlies inhibitory effects of Na+-free media on leukocyte function.
abstract: Inhibition of activation has been reported when neutrophils are suspended in Na+-free media. We considered the possibility that impairment of cellular pH (pHi) 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 pHi 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 neutrophils activation indirectly, by impairing pHi regulation.
mesh_terms: D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects; D009504:Neutrophils / Q000502:physiology*; D009550:Nigericin / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D011522:Protons; D012964:Sodium / Q000097:blood / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D011522:Protons; D012964:Sodium; D013755:Tetradecanoylphorbol Acetate; D009550:Nigericin; D011188:Potassium