n. any of a class of proteins that function as transmembrane water channels. Genetic mutations of aquaporin 2 (AQP-2) are responsible for some distinct forms of *nephrogenic diabetes insipidus.
(NDI) a condition characterized by *polyuria and *polydipsia and due to failure of the renal tubules to respond, or to respond fully, to *vasopressin. One form of congenital NDI is caused by an X-linked (see sex-linked) dominant mutation of the gene encoding the vasopressin V2 receptor. A rarer form of congenital NDI is an autosomal recessive condition associated with genetic mutations in the gene encoding AQP-2 water channels (see aquaporin). Acquired NDI is much commoner than the congenital form and usually less severe. It is present in most patients with advancing chronic renal failure, is a feature of certain electrolyte disorders (hypokalaemia, hypercalcaemia), and can complicate chronic lithium treatment.... nephrogenic diabetes insipidus
Health Encyclopedia