[Uptake of zinc-65 into mast cells after degranulation induced by copper disodium ethylendiamine tetraacetate]

Electron microscopic demonstration of metals in rat mast cells. A cytochemical study based on an improved sulphide silver method

This paper describes a modification of a cytochemical method for the demonstration of heavy metals. The well localized precipitate in the mast cell granules, which is also present in granules that have been separated from the cell, suggest that the metals are localized in the granules. It is demonstrated that "mast cell" grown cultures do not contain precipitate. The chelating and histamine inhibiting agent 8-hydroxyquinoline produced no changes in the histochemical pattern of the mast cell granules before nor after treatment with the histamine liberator 48/80 which provokes a release of granules from the cells. These observations suggest either that the metal (zinc) is bound to the granules in such a manner that the chelating agent cannot chemically, or based on the configuration of the metal-containing molecule, reach the metal and thereby prevent its transformation to a metal suphide.

No role for zinc in the storage of histamine in rat peritoneal mast cells

The histamine in the granules of mast cells has been proposed to be stored as a heparin-zinc-histamine complex. Due to its chelating action zinc should increase (double) the histamine binding capacity of heparin. We have determined the zinc content of isolated rat peritoneal mast cells to 2.4-4.1 nmol/10-6 cells and of their granules to 13.3-21.4 nmol/mg dry weight. The corresponding amounts of histamine were 150 and 680 nmol respectively. The zinc content found is far (20 times) too low to allow for an adequate binding of histamine in a heparin-zinc-histamine complex. In vitro the granules take up zinc in the same manner as they take up other cations and zinc competes with histamine for granule storage sites. Consequently, Hi-uptake is reduced and not enhanced in the presence of zinc in the suspension medium. In summary no evidence was found for a storage function of zinc in a heparin-zinc-histamine complex.