Inability of Ni++ and Co++ to release histamine from rat peritoneal mast cells

Ni++ and Co++ concentrations from 10 minus 3M to 10 minus 6M were added to rat peritoneal mast cells. These metal ions, at the concentrations indicated, did not cause histamine release from the mast cells, and did not inhibit the histamine release mediated by compound 48/80. On the basis of these studies, anaphylactoid edema of the rat following injection of i++ or Co++ is on a basis other than a direct effect of the m-tal ion on mast cells.