Removal of extracellular Ca stimulates histamine release from rat mast cells by mobilizing a labile cellular source of Ca.

Rat mast cells were stimulated by simultaneous removal of external Ca and Na, and their secretory mechanism was investigated. A brief EGTA-treatment of the cells markedly diminished this response with little affection the response to compound 48/80, suggesting that mobilization of Ca from labile pools in the membrane is involved in this response.