THE PREPARATION OF BOVINE NEUROPHYSIN AND THE ESTIMATION OF ITS MAXIMUM CAPACITY TO BIND OXYTOCIN AND ARGININE VASOPRESSIN

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Abstract
SUMMARY: The preparation is described of a hormone-binding protein fraction from bovine neurohypophyses (neurophysin). The fraction obtained by ion-exchange chromatography on CM-cellulose contained two components which were separated by gel filtration on Sephadex G-75; the property of binding oxytocin and arginine vasopressin was possessed by only one component of which the molecular weight was 25,000 approximately. The capacities of this protein to bind oxytocin and arginine vasopressin (each hormone in the absence of the other) were studied by a film dialysis method. The maximum binding capacities were 125 units of oxytocin/mg. protein and 62 units of arginine vasopressin/mg. protein, which are equivalent to seven molecules of oxytocin and four molecules of arginine vasopressin/molecule of protein (taken to the nearest whole numbers).