Vasopressin	

The main physiological role of vasopressin (ADH) is the reduction of free-water clearance by the kidney to produce concentrated urine. Vasopressin acts on the distal nephron to increase water permeability of the tubular cell so that solute-free water may pass along the osmotic gradient from the lumen of the nephron to the renal interstitial medulla. 

See later:
•ÊOther Effects of Vasopressin
• Regulation of Vasopressin Secretion
• Osmoregulation of Vasopressin Secretion and Thirst
• Plasma Osmolality and Plasma Vasopressin
•ÊBaroregulation of Vasopressin Secretion
• Renal Action of Vasopressin
• Analogues of Vasopressin