Exogenous vasopressin test

Evaluation of urine concentrating ability. Urine concentrating ability is determined using the water deprivation test or the exogenous vasopressin test. 

Water deprivation and exogenous ADH administration are two diagnostic tests that can be used to differentiate neurogenic from nephrogenic DI. The latter test is pursued only after there is a failure to produce concentrated urine in response to the water-deprivation test (Schott 1998). Until recently, the most commonly used form of exogenous ADH was a water-insoluble tannate of arginine vasopressin extracted from the posterior pituitary and suspended in peanut oil. This preparation is no longer available. Currently,... 

Once produced within the cell, c-AMP seems to have the activation of protein kinase as its main function. This activation in turn phosphorylates particular postsynaptic proteins in the cell membrane. This results in the alteration of pores facilitating cation passage. As a second messenger it facilitates the action of more than a dozen hormones besides NE/EP, including ACTH, insulin, lipotropin, calcitonin, and vasopressin. To the extent that they are tested experimentally hormonal effects could be mimicked by exogenous addition of c-AMP. 

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