IGE-RECEPTOR ACTIVATED CHLORIDE UPTAKE IN RELATION TO HISTAMINE-SECRETION FROM RAT MAST-CELLS

1 Antigen-stimulated histamine secretion from rat peritoneal mast cell s was inhibited when extracellular chloride was replaced by either ise thionate or gluconate anions, but the histamine release still remained quite substantial. 2 Rat peritoneal mast cells take up Cl-36 and the uptake reaches a steady state after 60 min incubation with the isotope . At steady state, the intracellular chloride level in the cells was c alculated to be 29 +/- 11.5 mM. 3 The chloride uptake in mast cells wa s exponential with a rate constant of 0.036 min-1 in resting cells. Wh en the cells were stimulated with antigen, and rate constant for chlor ide uptake increased to 0.90 min-1: an increase of 25 fold. Under iden tical experimental conditions histamine release increased 3 fold. 4 Th e rate of chloride uptake in either resting cells or in antigen-stimul ated cells was not changed when the extracellular medium was nominally calcium-free but histamine release was almost completely inhibited in the absence of extracellular calcium. 5 The putative chloride channel blocker DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid) 0. 3 to 30 muM, produced a concentration-related inhibition of antigen-st imulated histamine secretion but DIDS (30 muM) did not inhibit the ant igen-stimulated increase of chloride uptake. 6 The cyclic AMP analogue , dibutyryl cyclic AMP (1 mM) produced a delayed increase in chloride uptake in resting mast cells but neither dibutyryl cyclic AMP nor 8-br omo cyclic AMP per se induced any histamine secretion. 7 Ouabain (1 mM ) which inhibits the Na+/K+ ATPase in rat peritoneal mast cells, faile d to affect the uptake of chloride in resting mast cells. 8 The Na/K/2 Cl-cotransport inhibitor, furosemide (0.7 mM), slowed the unstimulated chloride uptake in resting mast cells and abolished the increased ant igen-induced chloride uptake when added together with antigen. In cont rast, spontaneous and antigen-induced histamine release were unaffecte d by the presence of furosemide. However, when furosemide was added to the cell suspension 5 min before stimulation, furosemide was without effect on the antigen-induced chloride uptake. 9 In addition to the ch loride uptake mediated by chloride channels which may be related to th e mechanism of histamine secretion, crosslinking of the high affinity membrane receptors for IgE is followed by a fast chloride uptake that is likely to occur through a furosemide-sensitive Na/K/2Cl-cotransport er.