Effect of benzamil on sheep tracheal epithelium.

Apical membrane potential (Va), voltage divider ratio (f), transepithelial potential (Vt) and transepithelial resistance (Rt) were measured in isolated sheep tracheal epithelium. Individual membrane resistances and electromotive forces were calculated by a method described in the text. Whereas Va hyperpolarized and fa increased in tissues acutely exposed to amiloride or benzamil, the values for these parameters in tissues bathed for 1 h with mucosal benzamil (0.38 microM) were not significantly different from those found in control tissues. Circuit analysis revealed a higher value for both apical and basolateral membrane resistances in the benzamil-treated tissues. These results suggest a decrease in the basolateral potassium conductance secondary to the initial decrease in the apical sodium conductance, thereby ensuring that the electrical driving force for other ions across the apical membrane is restored to normal in the face of a hyperpolarizing perturbation to the apical membrane.