The Effect of Diphenylamine-2-carboxylate on C1− Channel Conductance and on Excitability Characteristics of Rat Skeletal Muscle

Abstract

Abstract The effect of diphenylamine-2-carboxylate (DPC), a blocker of the C1− conductive pathway in C1− transporting epithelia, has been evaluated in-vitro on the electrophysiological variables of rat extensor digitorum longus muscle fibres. DPC (5–240 μM) caused a dose-related increase of membrane resistance which was attributed entirely to a fall in C1− channel conductance (IC50, 120 μM), since potassium conductance was not affected by the treatment. DPC also modified fibre excitability. A significant dose-dependent increase was observed in the latency of the action potential and in the excitability of the membrane. DPC was less potent on striated fibres than anthracene-9-carboxylic acid, another specific blocker of C1− channel conductance. Moreover DPC was less potent on skeletal muscle than on C1− transporting epithelia. Morphological differences in the C1− channels or of the drug binding sites may account for the differences between tissues.