Vasopressin, an aa kent as antidiuretic hormone (ADH), is a neurohypophysial hormone foond in maist mammals. In maist species it conteens arginine an is thus an aa cried arginine vasopressin (AVP) or argipressin. Its two primary functions are to retain water in the body and to constrict blood vessels. Vasopressin regulates the bouk's retention o watter bi actin tae increase watter reabsorption in the kidney's collectin ducts, the tubules which receive the very dilute urine produced bi the functional unit o the kidney, the nephrons. Vasopressin is a peptide hormone that increases watter permeability o the kidney's collectin duct an distal convolutit tubule bi inducin translocation o aquaporin-CD watter channels in the plasma membrane o collectin duct cells. It an aa increases peripheral vascular resistance, which in turn increases arterial bluid pressur. It plays a key role in homeostasis, bi the regulation o water, glucose, an sauts in the bluid. It is derived frae a preprohormone precursor that is seenthesised in the hypothalamus an stored in vesicles at the posterior pituitary. Maist o it is stored in the posterior pituitary tae be released into the bluidstream. Houever, some AVP mey an aa be released directly intae the brain, an accumulatin evidence suggests it plays an important role in social behaviour, sexual motivation an pair bondin, an maternal responses tae stress. It haes a very short hauf-life atween 16–24 minutes.