Effects of endotoxin and tannin isolated from cotton bracts on the airway epithelium.

The effects of increasing concentrations of tannin isolated from cotton bracts and endotoxin prepared from Enterobacter agglomerans on the electrophysiologic and ion transport properties of the canine tracheal epithelium mounted in Ussing chambers were examined. Results were compared with those obtained using cotton bracts extract (CBE). Tannin concentrations in the isolated tannin and in the cotton bracts were analyzed spectrophotometrically. When added to the mucosal bathing solution, tannin produced a significant decrease in transepithelial potential difference and short-circuit current (lsc) with a maximal response at 25 microliter. The decrease in lsc was accounted for entirely by a decrease in net chloride secretion. The effects were reversible and specific for the mucosal bathing solution. In contrast to CBE, tannin had no effect on mannitol flux, suggesting no effect on the paracellular pathway. Endotoxin at a concentration of 10 micrograms/ml had no effect on the electrophysiologic properties of the canine trachea. We conclude that tannin in CBE is responsible for the decrease in lsc observed with aqueous extracts of CBE but is not responsible for the changes in the paracellular pathway. We also conclude that endotoxin alone has no effect on the airway epithelium.