Spontaneous histamine release from isolarted Mastcells was found to be independent of cal­cium in the concentration range up to 1 m. mole/lit. Phosphatidyl serine do not change the effect of calcium on spontaneous release. The activation of anaphyla.ctic histamine release by calcium is potentiated by phosphatidyl serine but the laitter can't do so w1th strontium. 
Mastcells, pretreated with ATP, loose their sensitivity towards compound 48/80 but ithey will find their sensitivity after a while. This spontaneous restoration of Mastcells sensitivity towards 48/80 seems to be an energy - de­pendent process involving a factor, functioning through some mechanisms in the Mastcells. Such a fa.ctor could be a divalent cation, pre­sented in the Mastcells. Ultimately, pancuro­nium, should be mentioned, which is said to be histamine releasing stimulant.