In these experiments the effects of pharmacological concentrations of auranofin, a new absorbable gold compound, were assessed on the release of histamine and peptide leukotriene C4 (LTC4) from human basophils and lung mast cells. Auranofin, at pharmacological concentrations, inhibited in vitro histamine and LTC4 release from human basophils induced by anti-IgE. Inhibition began at about 3 X 10(-7) M and was maximum at 10(-5) M. We also evaluated the effect of auranofin on the release of histamine and LTC4 induced by anti-IgE from mast cells purified from human lung. Auranofin (3 X 10(-7) to 10(-5) M) dose-dependently inhibited the release of histamine and LTC4 from human lung mast cells. Thus pharmacological concentrations of auranofin cause dose-related inhibition of histamine release and de novo synthesis of LTC4 by human basophils and lung mast cells.