Aldosterone Contributes to Vasopressin Escape through Changes in Water and Urea Transport

Hyponatremia (hypo-osmolality) is a disorder of water homeostasis due to abnormal renal diluting capacity. The body limits the degree which serum sodium concentration falls through mechanism called “vasopressin escape”. Vasopressin escape process that prevents continuous decrease in even under conditions sustained high plasma vasopressin levels. Previous reports suggest aldosterone may be involved mechanism. abilities synthase (Cyp11b2) knockout and wild-type mice from were compared. Wild-type escaped while did not. Both channel aquaporin 2 (AQP2) urea transporter UT-A1 protein abundances higher than at end period. was also blunted rats given spironolactone, mineralocorticoid receptor blocker. Next, role phosphatase, calcineurin (protein phosphatase 2B, PP2B), studied since activates rat cortical collecting ducts. Tacrolimus, inhibitor, compared with control rats, increased UT-A1, AQP2, pS256-AQP2, decreased pS261-AQP2 abundances. Our results indicate regulates calcineurin-mediated changes AQP2.