Histamine release induced from rat mast cells by the ionophore A23187 in the absence of extracellular calcium

Isolated rat mast cells were used to study whether ionophore A23187 could induce histamine release by mobilizing cellular calcium. The histamine release was a slow process which was completed after about 20 min incubation with A23187. The A23187-induced histamine release was inhibited after incubation of the cells with EDTA for 1 h in a 37°C water bath in calcium-free medium. Reintroduction of calcium in excess of EDTA induced the release of histamine. The observations suggest that A23187 can induce histamine release by mobilizing a cellular pool of calcium.