Sequential analysis of histamine release and intracellular Ca²⁺ release from murine mast cells

Stimulation of murine peritoneal mast cells with compound 48/80 at a concentration of 1 ug/ml elicited rather slow histamine release; the onset of release was observed 5 s after stimulation, and it reached a plateau at about 60 s. Both inositol-1, 4, 5-trisphosphate (IP₃) and inositol-1, 4s-bisphosphate (IP₂) contents increased to their maximum 5 s after stimulation. The IP₃ content decreased to the control level more rapidly than that of IP₂. Changes in the intracellular Ca²⁺ concentration of the quin 2 loaded mast cells were determined using a video-intensified microscopy system. The fluorescence intensity due to Ca-quin 2 complex increased rapidly after 48/80 stimulation in a Ca-free medium and reached the maximum at about 6-7 s. It became clear that the increase in IP₃ content and the resulting Ca²⁺ release from the intracellular Ca store precede histamine release from murine mast cells.