FIG. 1.
Effect of P-301 and amiloride on epithelial sodium channel (ENaC) in primary cell culture system. Epithelial cells were isolated from excised canine bronchial tissue and cultured under conditions that promote a polarized monolayer. Cultures were mounted in modified Ussing Chambers and under voltage-clamped conditions, and short-circuit current (ISC) was measured as an index of transepithelial sodium transport. P-301 or amiloride was added to the apical side of the chambers at increasing concentrations, and the corresponding changes in ISC were measured. Using standard curve-fitting methods and goodness-of-fit assessments, the concentration of the compound needed to inhibit ISC by 50% (IC50 concentration) was calculated (n=40 for amiloride, n=11 for P-301).