In vitro inhibition of histamine release from mouse mast cells and human basophils by an anthranilic acid derivative.

Optimal conditions for in vitro histamine release mediated either by Con A (3 micrograms/ml) or by Ionophore A23187 (1 microgram/ml), were established for mouse peritoneal mast cells and human normal basophils. In both systems N-5' exerts potent inhibiting effects on histamine release after short term (1-5 minutes) in vitro preincubation. At concentrations of 1mM for mouse mast cells and 3mM for normal human basophils, N-5' inhibits up to 95% Con A-induced histamine release and more than 50% ionophore-induced histamine release. Such in vitro effects are more potent than DSCG-mediated inhibition, under similar experimental conditions, and are resistant to challenge with exceeding doses of the two releasing agents, particularly in the Con A system. Interestingly, basophils with apparent normal morphology, from a CML patient, were resistant to both challenges.