We set out to better understand the physiological role of Clc-k1 and Clc-k2 in the perinatal kidney, and we hypothesized that the developmental expression of Clc-k1 and Clc-k2 and their relative roles may shed light on the phenotypical variabilities and early pathogenesis of classic Bartter syndrome in some patients. Here, CLCNKB is linked to Bartter syndrome.