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Ionic regulation of human basophil releasability. III. Effects of Na+ and Ca2+ on histamine release induced by
A Tedeschi1, M Palella, M Arquati
1Department of Internal Medicine, University of Milan, Ospedale Maggiore Policlinico, Italy.
Abstract:
The effects of Na+ and Ca2+ ions on histamine release from human basophils stimulated by anti-IgE, N-formyl-methionyl-leucyl-phenylalanine (FMLP), 4 beta-phorbol 12-myristate 13-acetate (PMA) and Ca2+ ionophore A23187 were evaluated. Isosmotic replacement of Na+ in the extracellular medium with the nonpermeant 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 < 0.001), FMLP- (1 microM: 37.9 +/- 2.3% vs 49.5 +/- 4.3%, n = 8, P < 0.01) and PMA-(160 nM: 12.7 +/- 0.9% vs 27.3 +/- 4.3%, n = 8, P < 0.05) induced histamine release, whereas A23187-induced histamine release was reduced (1 microM: 90.4 +/- 2.4% vs 45.4 +/- 3.4%, n = 8, P < 0.0001). The progressive increase in extracellular Na+ 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 Ca2+ 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 anti-IgE, FMLP and PMA, whereas it enhances Ca2+ 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.