**3.2.6 Prolactin, dopamine and renalase**

Prolactin is also a natiriuretic hormone that inhibits Na+, K+, ATPase activity in PTCs, depending on the renal dopamine system (Ibarra et al. 2005). Dopamine is known to both acutely and chronically inhibit the function of NHE3 by reducing its cellular expression (Bobulescu and Moe 2009). Renalase, a secreted amine oxidase that is synthesized in the kidney, metabolizes circulating catecholamines (Xu et al. 2005). Urinary renalase metabolizes urinary catecholamines, and perhaps regulates dopamine concentration in luminal fluid, and modulate the function of NHE3 for proximal tubular sodium transport (Desir 2011).
