Aquaporins: Roles in renal function and peritoneal dialysis

Aquaporin (AQP) water channels are important in the function of the kidney. Constitutively expressed AQP1 in the proximal tubule and descending limb i s important in normal fluid absorption and in the counter-current multiplic ation system. The vasopressin-regulated shuttling of AQP2 is essential in a ntidiuresis and the regulation of water balance. Genetic damage to AQPs, or pathological changes in expression or function, impair renal water handlin g. The most striking examples of this involve disruption of AQP2 function, which can result in profound nephrogenic diabetes insipidus. Aquaporin 1 is present in capillaries and venules and appears to be important in peritone al dialysis, where it appears to represent the "ultrasmall pores" of the th ree-pore model. Decreased expression or function of AQP1 may be responsible for some cases of ultrafiltration failure, but further evidence will be re quired to establish whether this is the case.