Evidence for Intact V1-vasopressin Receptors in Congenital Nephrogenic Diabetes Insipidus
| Title: | Evidence for Intact V1-vasopressin Receptors in Congenital Nephrogenic Diabetes Insipidus |
|---|---|
| Authors: | Knoers, Nine; Janssens, P.M.W.; Goertz, J.; Monnens, Leo A.H. |
| Publisher: | European Journal of Pediatrics |
| Date Published: | May 01, 1992 |
| Reference Number: | 305 |
The binding of tritium-labelled arginine vasopressin to human platelet vasopressin receptors was investigated in patients with congenital nephrogenic diabetes insipidus. Binding characteristics, that is receptor affinity and the maximum number of binding sites, were not significantly different from those found in normal control individuals. The findings confirm the concept of intact V1-receptors in congenital nephrogenic diabetes insipidus. The defect in nephrogenic diabetes insipidus apparently only affects the cyclic adenosine monophosphate dependent V2 receptors.
This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)
Vasopressin-2 receptors (V2R) are located in the principal cells of the kidney collecting ducts and elsewhere outside the kidney. The V2Rs in the kidney regulate water reabsorption and urine concentration. The V2Rs outside the kidney help regulate the dilation of blood vessels and the release of certain blood coagulation factors and tissue-type plasminogen activators.
In congenital nephrogenic diabetes insipidus (NDI) the kidneys do not respond to the antidiuretic action of AVP, which means the NDI patient cannot concentrate urine or reabsorb the water flowing through the kidney collecting ducts. The primary symptoms of NDI are polyuria (chronic passage of large volumes of urine) and polydipsia (chronic, excessive thirst). The most common form of congenital NDI is X-linked, and the gene responsible for X-linked NDI is the mutated V2R gene. Both the V2Rs of NDI patients located within and without the kidney fail to respond to AVP, indicating a general malfunction of their V2Rs.
To test the assumption that NDI patients have normal, fully functional V1Rs, Knoers, et. al., examined the specific binding of AVP to V1R on blood platelets of four NDI patients and compared them to the binding of AVP to V1R in four healthy individuals. The binding characteristics were determined by measuring the V1Rs binding affinity with AVP and the maximum number of binding sites (i.e. V1Rs) found in the experimental laboratory cell cultures.
The researchers found no significant difference between the performance of V1Rs of the NDI patients and the control group in either binding affinity or maximum number of binding sites. This confirmed the presence of intact V1Rs in NDI patients and provides further evidence that the defect in X-linked NDI is in defective V2Rs.