[Common precursors of neurohypophysial hormones and neurophysins]

Neurohypophysial hormones and neurophysins are former domains of common precursors processed during the axonal transport from hypothalamus to neurohypophysis. Two neurohormones, an oxytocin-like and a vasopressin-like, and two neurophysins, termed VLDV- and MSEL-neurophysins according to residues in positions 2, 3, 6 and 7, are usually found in vertebrate species. In mammals, a non-covalent stoichiometric and reversible complex including the two neurohormones and the two neurophysins has been isolated. In contrast to other mammals investigated, the three-domain precursor of vasopressin (vasopressin, MSEL-neurophysin and copeptin) is not completely processed in guinea pig and an intermediate precursor including MSEL-neurophysin and copeptin linked by an arginine residue has been isolated and sequenced. "In vitro" processing of this intermediate through trypsin-Sepharose has revealed cleavages only in the inter-domain region, showing the role of precursor conformation in the processing. In neurosecretory granules from guinea pig, only free vasopressin and MSEL-neurophysin have been detected. In bovine foetus at the age of 3 and 7 months, only vasopressin and oxytocin in molar ratios 4 and 3, respectively, have been identified as well as adult MSEL- and VLDV-neurophysins. No vasotocin and no additional neurophysin when compared to the adult have been found. Diabetes insipidus rats from the Brattleboro strain have been examined in order to identify an abnormal vasopressin precursor. No free vasopressin and no free MSEL-neurophysin have been detected through high pressure liquid chromatography whereas oxytocin and VLDV-neurophysin have been identified.(ABSTRACT TRUNCATED AT 250 WORDS)