Antidiuretic hormones released by the NEUROHYPOPHYSIS of all vertebrates (structure varies with species) to regulate water balance and OSMOLARITY. In general, vasopressin is a nonapeptide consisting of a six-amino-acid ring with a cysteine 1 to cysteine 6 disulfide bridge or an octapeptide containing a CYSTINE. All mammals have arginine vasopressin except the pig with a lysine at position 8. Vasopressin, a vasoconstrictor, acts on the KIDNEY COLLECTING DUCTS to increase water reabsorption, increase blood volume and blood pressure.

A pharmaceutical preparation containing a mixture of arg-vasopressin and lys-vasopressin. It is prepared by synthesis or obtained from neurohypophyseal extract of domestic animals. Its vasopressor activity is not less than 300 USP vasopressin units per mg.

Synonyms: 0, beta-Hypophamine, Vasopressin (USP), beta Hypophamine, Hormone, Antidiuretic, Antidiuretic Hormones, Antidiuretic Hormone, 11000-17-2, Pitressin, Vasopressin, Vasopressins