Effect of cotton bracts extract on canine tracheal epithelium and shunt pathway

The effects of increasing concentrations (5 to 100 microliters) of an aqueous extract of cotton bracts (CBE) on the electrophysiologic properties and paracellular pathway of the canine trachea mounted in Ussing chambers were examined. The CBE produced a 50% decrease in short-circuit current and a dose-dependent decrease in transepithelial potential difference and tissue resistance when added to the mucosal bathing solution. The decrease in tissue resistance after exposure to 25 and 100 microliters was followed by an increase in mannitol flux, suggesting an effect on the paracellular pathway. No significant effect on mannitol flux was seen after 5 microliters CBE, when results were compared with control tissues from the same dog. The effects of 5 microliters CBE but not higher concentrations were reversible. Submucosal CBE had no effect on the electrophysiologic properties of the canine trachea or on mannitol flux. We conclude that in the canine tracheal epithelium, CBE inhibits active ion transport, alters the paracellular pathway, and acts only from the luminal surface.