Aquaporin-2, a vasopressin-sensitive water channel, and nephrogenic diabetes insipidus.

Two cases of autosomal recessive nephrogenic diabetes insipidus (NDI) were evaluated. Both cases were found to be compound heterozygote for missense mutations in the aquaporin-2 (AQP2) gene. To determine the structural-functional relationship, the mutated AQP2 proteins, T125M, G175R, A190T, and P262L, were expressed in Xenopus oocytes and examined by measurement of water permeability, immunoblot, and immunocytochemistry. Our results suggest that T125M and G175R are nonfunctional water channels, whereas the translocation to the plasma membrane is impaired in A190T and P262L.