The distribution of proteins that bind neurohypophysial hormones.

1. Protein fractions were prepared from serum and various organs of pigs following the methods used to extract and purify neurophysin from posterior pituitaries.2. Protein fractions extracted from porcine kidney, uterus, mammary gland or serum, which contain antigen reacting with anti-neurophysin serum, form non-dialysable complexes with oxytocin and/or lysine vasopressin.3. Protein from uterus or mammary gland bound oxytocin but not lysine vasopressin, while protein extracted from kidney bound lysine vasopressin but not oxytocin: protein from serum bound both hormones.4. Protein fractions prepared in the same way from porcine liver, spleen, skeletal muscle and brain, which do not contain antigen reacting with anti-neurophysin serum, did not form complexes with neurohypophysial hormone.5. The formation of complexes between the renal or uterine protein fractions and lysine vasopressin or oxytocin is inhibited by the addition of 1.0 x 10(-6)M-CaCl(2).6. 1-Desamino 8-arginine vasopressin is not bound by neurophysin prepared from porcine posterior pituitaries or the protein from porcine kidneys, while 8-arginine vasopressin does form non-dialysable complexes with proteins from both sources.7. A protein fraction extracted from guinea-pig kidney by similar preparative methods also bound lysine vasopressin and the binding was inhibited by addition of CaCl(2).