External anions relieve DIDS inhibition of SO4 efflux from placental membrane vesicles

Abstract
Sulphate efflux from human placental microvillus membrane vesicles was inhibited by external DIDS (KI≅10−6 M). This inhibition was partially reversed on addition of the translocated substrates sulphate or selenate to the external medium: selenite which is not translocated does not protect against DIDS inhibition. These findings show that the mechanism responsible for sulphate efflux can be modified by substrate in the external medium.