Studies on the purification of lysine vasopressin from hog pituitary glands.

Previous work from this laboratory (1, 2) has demonstrated that the vasopressin from beef posterior pituitary lobes, after partial purification by the procedure of Kamm et al. (3), can be obtained in a high degree of purity by means of countercurrent distribution with the system 0.09 M p-toluenesulfonic acid-n-butyl alcohol. Although no detectable difference was observed in the physical properties or chemical composition of oxytocin prepared from either beef or hog posterior pituitary glands (4), Popenoe, Lawler, and du Vigneaud (5) observed a considerable difference between the partition coefficients, in the solvent pair mentioned above, of the vasopressins, depending upon whether they were obtained from hog or beef glands. The vasopressin obtained from beef glands contained arginine as one of its eight constituent amino acids, while, in the vasopressin from hog glands, lysine was present instead of arginine, the remaining seven amino acids being the same as those in the vasopressin from beef glands. The two vasopressins have been called arginine vasopressin and lysine vasopressin (5). In the preliminary work on lysine vasopressin, it was believed that some inactivation had occurred during the isolation of the material, and therefore it was suggested that the potency of the best product at that time (175 pressor units per mg.) was probably not the maximal potency of lysine vasopressin (5). The present work represents further studies on the purification of lysine vasopressin which have resulted in preparations of considerably higher potency. Desiccated hog posterior pituitary glands (powdered) are first fractionated according to the procedure of Kamm et al. (3), and then subjected to electrophoresis on powdered cellulose with pyridine acetate as a volatile buffer. The pressor material thus obtained is further purified by countercurrent distribution between either 0.1 per cent acetic acid-see-butyl alcohol or 0.08 M p-toluenesulfonic acid-set-butyl alcohol. The highest potency obtained in the present experiments is 235 to 255 pressor units per mg.