Antigen-stimulated histamine secretion from rat peritoneal mast cells was inhibited when extracellular chloride was replaced by either isethionate or gluconate anions, but the histamine release still remained quite substantial. 2. Rat peritoneal mast cells take up 36Cl 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 calculated to be 29 +/- 11.5 mM. 3. The chloride uptake in mast cells was exponential with a rate constant of 0.036 min-1 in resting cells. When the cells were stimulated with antigen, and rate constant for chloride uptake increased to 0.90 min-1: an increase of 25 fold. Under identical experimental conditions histamine release increased 3 fold. 4. The rate of chloride uptake in either resting cells or in antigen-stimulated 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 microM, produced a concentration-related inhibition of antigen-stimulated histamine secretion but DIDS (30 microM) did not inhibit the antigen-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-bromo cyclic AMP per se induced any histamine secretion. 7. Ouabain (1 mM) which inhibits the Na+/K+ ATPase in rat peritoneal mast cells, failed to affect the uptake of chloride in resting mast cells. 8. The Na/K/2C1-cotransport inhibitor, furosemide (0.7 mM), slowed the unstimulated chloride uptake in resting mast cells and abolished the increased antigen-induced chloride uptake when added together with antigen. In contrast, spontaneous and antigen-induced histamine release were unaffected 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 chloride uptake mediated by chloride channels which may be related to the 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/2C1-cotransporter.
