Kidney diabetes insipidus related

Other aquaporins with related sequences occur broadly. There are at least ten in mammals.359,3593 Plants, which must accommodate to heavy loss of water in hot dry weather, have aquaporins in both plasma membranes and tonoplasts.360 Bacteria also have aquaporins.356,361 A defect in aquaporin-2 of the kidney collecting duct leads to nephrogenic diabetes insipidus, in which the kidneys fail to concentrate urine in response to secretion of the hormone vasopressin.3553 362,363... 

Vasopressin [vay soe PRESS in] (antidiuretic hormone, ADH), is structurally related to oxytocin (Figure 25.5). The chemically-synthesized nonapeptide has replaced that extracted from animal posterior pituitaries. Vasopressin has both antidiuretic and vasopressor effects. In the kidney it binds to the V2 receptor to increase water permeability and resorption in the collecting tubules. Thus the major use of vasopressin is to treat diabetes insipidus. It also finds use in controlling bleeding due to esophageal varices or colonic diverticula. Other effects of vasopressin are mediated by the Vi receptor, found in vascular smooth muscle, liver and other tissues. As might be expected the major toxicity is water intoxication and hyponatremia. Headache, bronchoconstriction and tremor also can occur. Caution must be used in treating patients with coronary artery disease, epilepsy and asthma. 

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