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Calcium triggers the secretion of histamine from mast cells after previous exposure of the cells to sodium fluoride. The secretory process can be divided into a fluoride-activating step and a calcium-induced secretory step dependent on cellular metabolic energy. The secretory response induced by compound 48/80 in the absence of extracellular calcium was found to decrease after fluoride pretreatment of the cells. The response was, however, unaffected, provided calcium was introduced to the cells simultaneously with compound 48/80.

The effect of different concentrations of zinc ions on the in vitro release of histamine from isolated rat peritoneal mast cells induced by compound 48/80 and Triton X-100, as well as the influence of the in vivo administration of zinc ions on the subsequent in vitro release of histamine from isolated peritoneal mast cells and lung tissue, have been investigated. The results show that intraperitoneal administration of zinc for 20 days significantly inhibited the spontaneous ~elease of histamine from lung tissue as well as that induced by a low dose of compound 48/80. The in vitro addition of zinc ions to isolated mast cells significantly inhibited the release of histamine induced by low doses of compound 48/80 but not by high doses or by Triton X-100. Inhibition of histamine release increased up to 100 % with increase in the zinc ions concentration up to 10 -3 M. An inhibition of the histamine release from mast cells and lung tissue from animals which had received in vivo injection of zinc was also observed.The results indicate that the inhibitory action of zinc ions on the release of histamine is connected with an action on the biomembrane rather than on the histamine binding within the mast cells.