Inhibitory effect of traxanox sodium on IgE-mediated histamine release from passively-sensitized mast cells of the rat in vitro.

Traxanox sodium, a benzopyranopyridine derivative showing a potent oral antiallergic activity in the rat, was compared with disodium cromoglycate (DSCG) for ability to block the release of histamine from the rat mast cell in vitro. Traxanox sodium showed dose-, antigen- and time-dependent inhibiton of the IgE-mediated release of histamine. The 50% inhibitory concentration was 0.04 microM for traxanox sodium, 1 microM for DSCG and 660 microM for theophylline. All these drugs blocked the release of histamine potentiated by preincubation of the mast cell with 10 micro M adenosine at lower concentrations than those which could inhibit the IgE-mediated histamine release. In addition, traxanox sodium at concentration of 1-100 microM inhibited the histamine release caused by 0.25 microgram/ml compound 48/80 in the presence and absence of calcium, and the drug at 100 micro M slightly inhibited the release caused by 0.2 microgram/ml ionophore A23187. These results suggest that traxanox sodium is a more potent inhibitor than DSCG on the histamine release from the mast cells of the rat, and a part of its antiallergic action is due to a selective inhibition of the immunological release of allergic mediators from the mast cell.