Identification of neurohypophysial hormones with their antisera

Identifying posterior pituitary hormones in body fluids or neurohypophysial extracts was heretofore partially achieved by using pharmacologic potency ratios or semispecific inactivation by thioglycolate or enzymes. Production of antisera against oxytocin and lysine-vasopressin has prompted us to test their specificity against lysine-vasopressin, arginine-vasopressin, arginine-vasotocin, and oxytocin. In ethanol anesthetized rats, antidiuretic and milk-ejection activities were assayed for each peptide-antiserum combination after 0, 30, 60, and 90 min of incubation. Results indicate that (a) oxytocin antiserum inactivates oxytocin, but not arginine-vasopressin, lysine-vasopressin, or arginine-vasotocin; vasopressin antiserum inactivates arginine-vasopressin and lysine-vasopressin, but neither oxytocin nor arginine-vasotocin; (b) an identifiable antigenic site exists for each hormone; (c) relatively specific identifications of natural neurohypophysial peptides are possible using antisera and bioassays; (d) this method is promising for identifying neurohypophysial peptides in body fluids and pituitary extracts; and (e) active and passive immunization against oxytocin and vasopressin may increase our understanding of their physiologic functions.