Intracellular ion exchange between cytoplasmic potassium and granule histamine, an integrated link in the histamine release machinery of mast cells*

Abstract

Rat peritoneal mast cells isolated by gradient centrifugation in Percoll were placed between two membrane filters in a Sartorius filter apparatus and superfused with isotonic balanced salt solutions or with deionized isotonic sucrose. Histamine was released according to ion exchange kinetics. Our explanation of the observed phenomena is as follows. The superfusion induces a flow of cytoplasmic K+ ions across the histamine-containing granules, resulting in an ion exchange K+ in equilibrium Hi+ ions at the histamine binding sites. The concomitant equimolar outflow of histamine and potassium is considered to be due to a functional interplay between two histamine pools, a release and a donor pool. As the result of the K+ in equilibrium Hi+ ion exchange at the histamine binding sites of the release pool, these sites become transiently occupied by K+ ions only to be immediately reoccupied by Hi+ ions from the donor pool. The observed equimolar outflows are consistent with a 1/1 molar ratio in the exchange between histamine and potassium ions. The essential role of cytoplasmic potassium in the histamine release mechanism is a new and important observation with possible implications not only as to histamine release in general (including so-called 'spontaneous' histamine release) but also as to the release of biogenic amines and other positively charged substances stored in granules in ionic linkage to the matrix.

Juxtacellular histamine concentration governs histamine release from rat peritoneal mast cells

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Isolated rat peritoneal mast cells release histamine when superfused with isoosmotic salt or sucrose solutions. The release was ascribed by us to an intracellular ion exchange between potassium and histamine at granule sites, resulting from a flux of cytoplasmic potassium across the granules secondary to the disturbance of the 'state of equilibrium ' at the cell surface caused by the superfusion (Uvnas et al 1989). In the present article is shown that the histamine releasing effect is counteracted by the addition of histamine to the superfusion fluid.

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“…(mainly Na+ ions) in the extracellular fluid. However, we recently reported on a role for cytoplasmic potassium in the machinery of histamine release from mast cells (Uvnas et al 1989). Superfusion of isolated rat peritoneal mast cells with salt or sucrose solutions, isoosmotic with physiological saline, induced an efflux of histamine accompanied with a simultaneous, approximately equimolar efflux of potassium.…”

“…In our previous paper (Uvnas et al 1989) we ventured the hypothesis that the histamine efflux from superfused mast cells was due t o a disturbance of the existing 'state of equilibrium ' a t the mast cell surface. I n the present paper will be described a concentration-dependent inhibition of the histamine efflux o n the addition of histamine in p~ concentrations t o the super- C ml potassium releases have been described in previous reports (Uvnas et al 1985(Uvnas et al , 1986(Uvnas et al , 1989 and are therefore only briefly dealt with here. Peritoneal mast cells from five rats were isolated by gradient centrifugation in Percoll, transferred to a Sartorius filter apparatus and spread as homogenously as possible on a filter not allowing granules and cells to pass through (Schleicher and Schuell NL 16, 0.2 p m thick).…”

“…Releuse kinetics. The kinetics of histamine and potassium effluxes were determined and characterized as described previousll- (Uvnas et a/. 1989).…”

“…Inhibition of histamine release from supersmall variations between individual experiments fused mast cells by addition of histamine to the in number of mast cells and amounts of releasable superfusion fluid (isoosmotic, 0.32 M deionized sucrose, p~ 7, 0.2 m~ temperature), histamine could not be avoided. Since, however, Note that even under inhibitory influence the per-the histamine release Was quantitatively corsistent histamine release occurs according to ion related to the potassium content of the mast cell exchange kinetics (Uvnas et al 1989). we used the potassium 0 2figures as reference values for quantitative estimations of the concentration-dependence of the inhibitory action of external histamine.…”