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 microgram/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-1,4-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.