Effect of the Aquaretic Tolvaptan on Nitric Oxide System

Tolvaptan is a selective vasopressin receptor antagonist (V2R) that increases free water and sodium excretion. Inhibition of V2R increases vasopressin concentration in plasma, which stimulates V1-receptors in the vascular bed and may change both central and brachial hemodynamics and plasma concentration of vasoactive hormones. The purpose of the study is to measure the effects of tolvaptan on renal handling of water and sodium, systemic hemodynamics and vasoactive hormones at baseline and during nitric oxide (NO)-inhibition with L-NG-monomethyl-arginine (L-NMMA) in patients with autosomal dominant polycystic kidney disease.