Degranulation of Isolated Rat Mast Cells Induced by Adenosine Triphosphate in the Presence of Calcium Ions

An Analysis of the Site of Action by Means of Microelectrophoresis

Abstract

By means of electrophoretic micropipettes, ATP and Ca²⁺ were separately applied to the isolated rat mast cell, extra- and intracellularly. When ATP was applied close to the mast cell membrane, in the Ca²⁺-containing medium, a local degranulation was caused at the site of application. Generalized phenomena such as swelling and derangement of the inside structures were also frequently seen. A similar degranulation and morphological changes were elicited by the topical application of Ca²⁺, when the mast cell was incubated before with ATP in Ca²⁺-free medium. Intracellular application of ATP as well as of Ca²⁺ in the Ca²⁺-free medium did not cause degranulation at all, while degranulation was rarely caused by the ATP application when the medium contained Ca²⁺. Intracellular Ca²⁺ application was inert for degranulation even after the treatment with ATP in Ca²⁺-free medium.