Renal sulfate transport at the basolateral membrane is mediated by anion exchange.

Abstract

The transport of sulfate was studied in basolateral membrane (BLM) vesicles isolated from rat kidney cortex by centrifugation on a Percoll self-generating gradient. In contrast to sulfate transport at the luminal membrane, sulfate uptake by BLM vesicles was not Na dependent. Imposition of an inside > outside HCO3- gradient stimulated BLM sulfate uptake nearly 10-fold and produced a transient overshoot of about 4-fold. This process appeared to be come saturated at high concentrations of either HCO3- or sulfate. Sulfate itself, thiosulfate, and H- but not Cl or thiocyanate, were able to substitute for HCO3-. None of these anions was as effective as HCO3-. The sulfate/HCO3 exchange was unaltered by manipulation of membrane potential, suggesting that it was electroneutral. Both HCO3- stimulation and overshoot could be prevented by known inhibitors of anion transport, including mercuric chloride, 4-acetamido-4''-isothiocyanostilbene-2,2''-disulfonic acid, and phloretin. HCO3--stimulated sulfate uptake also was inhibited by thiosulfate, probenecid, and acetazolamide. Rat kidney BLM vesicles showed carrier-mediated anion exchange; this carrier may participate in both reabsorptive and secretory sulfate transport.