SLC12A3 and Bartter syndrome: Bartter syndrome is due to impaired function of the Na+-K+-2Cl– cotransporter (NKCC2) in the thick ascending limb (TAL) of the loop of Henle, whereas Gitelman syndrome is due to impaired function of the Na+-Cl– cotransporter (NCC) in the distal convoluted tubule (DCT) (3–6).