Regulation of AQP2 in Collecting Duct : An emphasis on the Effects of Angiotensin II or Aldosterone.

Vasopressin, angiotensin II (AngII), and aldosterone are essential hormones in the regulation of body fluid homeostatsis. We examined the effects of AngII or aldosterone on the regulation of body water balance. We demonstrated that 1) short-term treatment with AngII in the primary cultured inner medullary collecting duct cells played a role in the regulation of AQP2 targeting to the plasma membrane through AT1 receptor activation. This potentiated the effects of dDAVP on cAMP accumulation, AQP2 phosphorylation, and AQP2 plasma membrane targeting; 2) pharmacological blockade of the AngII AT1 receptor in rats co-treated with dDAVP and dietary NaCl-restriction (to induce high plasma endogenous AngII) resulted in an increase in urine production, a decrease in urine osmolality, and blunted the dDAVP-induced upregulation of AQP2; 3) long-term aldosterone infusion in normal rats or in rats with diabetes insipidus was associated with polyuria and decreased urine concentration, accompanied by decreased apical but increased basolateral AQP2 labeling intensity in the connecting tubule and cortical collecting duct; and 4) in contrast to the effects of dDAVP and AngII, short-term aldosterone treatment does not alter the intracellular distribution of AQP2. In conclusion, angiotensin II, and aldosterone could play a role in the regulation of renal water reabsorption by changing intracellular AQP2 targeting and/or AQP2 abundance, in addition to the vasopressin.