ROLE OF CELL-FIXED CALCIUM IN HISTAMINE-RELEASE BY COMPOUND 48/80

Histamine release by compound 48/80 was substantially reduced in a time‐dependent manner (maximum at 30 min) by pre‐incubating mast cells in calcium‐free medium at 37°C but not at 2°C. This effect was optimal at pH 7.0 to 7.5. The re‐introduction of calcium (0.1 to 3 mmol/1) restored histamine release to the control value; this effect was independent of temperature. Strontium (1 to 30 mmol/1) partially reversed the effect of calcium deprivation but the same concentrations of barium and magnesium depressed histamine release even further. Magnesium (3 to 15 mmol/1) antagonized the effect of calcium replacement. Results suggest that the level of cell‐fixed calcium involved in compound 48/80‐induced histamine release may be controlled by the combinaton of rapid passive influx and slow active efflux. 1979 British Pharmacological Society