Gold-induced reduction in reactivity to histamine in isolated guinea pig tracheal rings

Direct effects of gold preparations on the smooth muscle were investigated on isolated guinea pig tracheal rings. Pretreatment of the tracheal rings for 150 min with 100 microM of gold sodium thiomalate [Au(I)] significantly reduced the contraction heights induced by 4.5 microM histamine from 0.24 +/- 0.02 to 0.14 +/- 0.01 g (p less than 0.01). Gold chloride [Au(III)] was far more potent in its inhibitory effects than gold sodium thiomalate. With 15 min preincubation, gold chloride significantly suppressed the histamine-induced contraction (p less than 0.05) at such a low concentration as 10 microM (3.4 micrograms/ml). Gold chloride as well as gold sodium thiomalate did not interfere with the ciliary motion of the tracheal epithelium, whereas colchicine, having no effect on the histamine-induced contraction, did interfere with ciliary motion. These results reveal that gold itself inhibits noncaustically the guinea pig tracheal contraction induced by histamine.