CHARACTERIZATION OF THE CHLORIDE CONDUCTANCE IN PORCINE RENAL BRUSH-BORDER MEMBRANE-VESICLES

The chloride conductance in brush-border membrane vesicles prepared fr om pig kidney cortex was investigated using a light-scattering assay, anion-diffusion-potential-dependent Na+-D-glucose cotransport and Cl-3 6- influx. K+-diffusion-potential-driven salt exit from, or entry into , the vesicles was slow in the presence of gluconate, SO42- and F-, in termediate with Cl- and Br- and fast with I-, NO3-, and SCN-. Stimulat ion of Na+-D-glucose uptake followed a similar anion sequence. Conduct ive Cl- flux had a low activation energy and was inhibited by suphhydr yl reagents, the stilbene disulphonates tamido-4'-isothiocyanatostilbe ne-2,2'-disulphonate (SITS) and 4,4'-diisothiocyanato-2,2'-disulphonat e (DIDS), and the arylaminobenzoates diphenylamine-2-carboxylic acid ( DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). Intravesi cular Ca2+ and extravesicular nucleotides were without effect on condu ctive Cl- flux. These characteristics tentatively exclude some known C l- channels and leave members of the ClC family as possible candidates responsible for the Cl- conductance in brush-border membranes.