[Nephrogenic diabetes insipidus]

Nephrogenic diabetes insipidus (NDI) is a rare disease characterized by polyuro-polydipsic syndrome (> 30 ml/kg/day in adult) related to an inability to concentrate the urine secondary to resistance to the antidiuretic action of vasopressin (AVP) or to its V2 agonist, dDAVP. NDI may be congenital or acquired. Congenital NDI, familial in most cases, are related in 90% of cases to mutations of the gene coding for V2 receptor of AVP (X-linked recessive disease), and in 10% of cases, to mutations of the gene encoding for aquaporin 2 (autosomic recessive disease). This water channel is expressed at the apical membrane of principal cells of collecting ducts and mediates water transport across the apical plasma membrane of these cells. It is regulated by AVP in two ways. First, AVP has a short term effect in triggering translocation of aquaporin-2-containing intracytoplasmic vesicles to the apical membrane. Second, AVP has a long term effect in increasing the expression of aquaporin-2 in collecting duct. Acquired NDI are iatrogenic (lithium), or related to electrolytic (hypokalemia) or renal abnormalities. The mechanism of these acquired NDI is a decrease of aquaporin 2 abundance in the renal collecting duct.