The effects of Na+ and Ca2+ ions on histamine release from human basophils stimulated by anti-IgE, N-formyl-methionyl-leucyl-phenylalanine (FMLP), 4β-phorbol 120myristate 13-acetate (PMA) and Ca2+ ionophore A23187 were evaluated. Isosmotic replacement of Na+ in the extracellular medium with the non-permeant Na+ analogue choline+ or with glucose led to a significant increase in anti-IgE- (1/5000: 43.7±7.3% in high Na+ vs 68.9±7.3% in low Na+ mean±sem, n=8, P+ concentration was accompanied by a decrease of basophil response to anti-IgE, FMLP and PMA; in contrast, A23187-induced histamine release was up-regulated by Na+ The Na+/H+ exchanger monensin, in the concentration range of 10-8-10-4 M, exerted a dose-dependent inhibitory effect on anti-IgE-, FMLP- and PMA-induced histamine release, but not on A23187-induced histamine release. Extracellular Ca 2+ up-regulated the histamine release induced by all the above stimuli. Removal of extracellular Na+ lowered the requirement of extracellular Ca2+ for anti-IgE, FMLP- and PMA-induced histamine release. In contrast with previous observations showing that Na+ supports histamine release from rat peritoneal mast cells and rat basophilic leukaemia cells, these results indicate that Na+ strongly inhibits histamine release from human basophils stimulated by antiIgE, FMLP and PMA, whereas it enhances Ca 2+ ionophore A23187-induced histamine release. The effects of Na+ which are probably related to modulation of membrane potential and/or intracellular pH, vary depending on the cell type and the stimulus employed for cell activation.
- histamine release
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