Voltage-dependent block of the cystic fibrosis transmembrane conductance regulator Cl- channel by two closely related arylaminobenzoates

Permeation properties of the cystic fibrosis transmembrane conductance regulator (CTFR) were studied with the aid of diphenylamine-2-carboxylate (DPC) and flufenamic acid (FFA) blocking agents. The blockade is dependent on voltage, affecting currents at positive potentials alone, which implies an open-channel block. Depolarizing membrane voltages cause continuous bursts for up to ten seconds, hyperpolarizing voltages cause interrupted bursts. Vm flickers attested to the permeation of drugs through the membrane. The binding site for both drugs was the same FFA and DPC voltage-dependent blockage aid in the study of CTFR structure-functions.