Abstract
Procedures for the local application of chemical agents to individual rat peritoneal mast cells are described. The local application of adenosine triphosphate (ATP) to the mast cell surface did not induce degranulation of the cell, a process known to occur concomitantly with histamine release induced by compound 48/80 and antigen-antibody reactions. Instead, reversible configurational changes of the cell membrane gradually occurred without any striking changes in the over-all cell volume. Swelling was observed after incubation of mast cells with ADP as well as by intracellular electrical manipulations with pipettes filled with H3PO4. The reversal of swelling was also demonstrated. The results are discussed in relation to the known histamine-releasing effect of ATP on rat mast cells and the difference in the mechanisms of histamine release induced by ATP and degranulating agents are stressed.