Novel mechanisms for NaCl reabsorption in the collecting duct

Purpose of review There is consensus that the abnormal retention of sodium by the kidney is the most important pathophysiological event in hypertension. The present review summarizes our current understanding of sodium reabsorption in the distal nephron. Recent findings The antihypertensive effect of thiazides is thought to be mediated by inhibiting Na+ uptake via the NaCl cotransporter NCC in the distal convoluted tubule. Although it was known that thiazide-sensitive Na+ reabsorption in isolated cortical collecting ducts can occur independently of the epithelial Na+ channel ENaC, its molecular correlate was unresolved. It was absent in isolated cortical collecting ducts of mice with a targeted disruption of the Na+-driven chloride/bicarbonate exchanger NDCBE suggesting that this pathway involves apical Na+ uptake into intercalated cells via the Na+-driven anion-exchanger NDCBE (SLC4A8). Summary The finding that SLC4A8-dependent thiazide-sensitive Na+ reabsorption occurs in the cortical collecting duct challenges our current model of how thiazides mediate their antihypertensive action and identifies a potentially new target for antihypertensive strategies.