Vasopressin plays a crucial role in the ability of the kidney to concentrate urine. In the last 3 to 4 years, a renewed interest in vasopressin has emerged, because of availability of selective, orally active antagonists of the different vasopressin receptors and of an immunoassay for the measurement of copeptin, a surrogate marker of vasopressin.
All solutes are not concentrated equally in the urine. The concentration of urea and of other nitrogenous end-products accounts for most of the solute-free water reabsorbed by the kidney. The concentration of these wastes represents a burden for the kidney because it operates at the expense of a less efficient excretion of several solutes and induces a significant hyperfiltration and increased metabolic demand. These consequences of vasopressin action may participate in kidney disease progression.