Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a recently described entity, linked to gain-of-function mutations (R137C and R137L) in arginine vasopressin (AVP) gene leading to chronic activation of tubular V2 AVP receptor (V2R) and thus free water reabsorption. In addition to collecting duct cells, the V2R is also expressed in endothelial cells, where it mediates the rise in circulating levels of von Willebrand factor (vWF) and coagulation factor VIII (fVIII).Background
Recent in vitro data showed that these mutant receptors are resistant to vasopressin-stimulated cAMP production. We aimed to explore by clinical observations the sensitivity to vasopressin of the R137C–V2R mutant in vivo.Material and methods
We performed a stimulation test with 1-desamino-d arginin vasopressin (dDAVP) 0·3 μg/kg of bodyweight in three patients (two hemizygous male and one heterozygous female) with NSIAD with R137C mutation and measured on the one hand the levels of vWF and fVIII and the other hand urine osmolality and albumin excretion (UAE).Results
Whereas the female heterozygous patient displayed normal response to simulation by dDAVP (except for UAE), no increase in vWF, fVIII, urinary osmolality and UAE was observed among hemizygous male patients.Conclusions
Coherent with in vitro observation in transfected cells, our clinical observations demonstrate that the R137C–V2R mutant is resistant to vasopressin stimulation in its physiological sites of expression.