Fig. 1.

Molecular physiology of salt transport in TAL. Five genes are known to be the cause of Bartter syndrome type I to type V as stated. By acting in a Gαs-coupled receptor, vasopressin or parathyroid hormone increases cAMP production which in turns increases the activity of NCCC2 and ROMK, thereby augmenting salt reabsorption. In contrast, by acting in a Gαq-coupled receptor, extracellular Ca²⁺ inhibits, both NKCC2 and ROMK, decreasing salt reabsorption