Purification of oxytocin and vasopressin by way of a protein complex.

In this laboratory we have previously employed, as a preliminary step in the isolation of oxytocin and vasopressin from posterior pituitary glands (l-3), the method introduced by Kamm et al. (4) for obtaining a fraction high in oxytocic activity and another high in pressor activity. Further purification involved the use of countercurrent distribution (l-3) and zone electrophoresis (3). We have recently observed in a chromatographic study of certain active fractions prepared according to Kamm that the contaminants behave mainly in the same manner as does peptide material (5). It may be recalled that posterior pituitary tissue has a high peptide content (6, 7), and this fact may explain some of the difficulties encountered in the isolation of oxytocin and vasopressin by our own (l-3) and other methods (8, 9). In 1940, Rosenfeld (10) concluded, from the results of sedimentation studies in the ultracentrifuge, that the pressor and osytocic principles existed in untreated press-juice of the posterior lobe of the pituitary in the form either of a single large molecule or of two separate large molecules similar in their sedimentation properties. In 1942, van Dyke and his associates (11) reported the isolation under mild conditions of an apparently homogeneous protein from posterior pituitary lobes which had osytocic and pressor activities in a ratio of approximately 1 :l. Acher, Chauvet, and Olivry (12) reported in 1956 that the activities of the “van Dyke protein” are due to oxytocin and vasopressin which can be dissociated from the protein complex by countercurrent distribution, TCAl precipitation, clectrophoresis, or dialysis against dilute acid, but it cannot be dissociated from it by dialysis against water, ultrafiltration, or precipitation by sodium chloride. The possible biological significance of the complex has been discussed recently by van Dyke, Adamsons, and Engel (13) and by Acher and Fromageot (14). However, regardless of its biological role, it seemed possible tlrat the protein complex might prove to be an effective tool in the isolation of oxytocin and vasopressin, particularly from small amounts