Preparation of high potency oxytocic material by the use of counter-current distribution.

The active principles of the posterior lobe of the pituitary gland have been separated and concentrated in several different laboratories by a variety of procedures. In a recent review (1) the details of many of these procedures and the potencies of the products obtained have been compared. Among the methods used for separating and concentrating the oxytocic and pressor factors, differential precipitation has been the most widely used. Electrophoresis of active material has been used effectively in concentrating the pressor factor (2), but this technique has not yet been applied to the purification of the oxytocic substance. The pressor and oxytocic factors have also been separated by chromatographic adsorption (3). Further purification (4) of the material eluted from the chromatographic column has yielded pressor and oxytocic mat.erial having a higher potency than that obtained by any of the other methods used up to that time. Although the various concentration procedures have yielded oxytocic and pressor material of quite high potency, there has been no evidence that any of the preparations have been pure. In this Laboratory the counter-current distribution technique of Craig (5) has recently been applied to the purification of the oxytocic factor. By the use of this technique much inert material has been removed, and there is some evidence that the most potent preparations obtained by this method may be very nearly pure. Starting with material having a potency of 20 units per mg., a product having an activity of 850 units per mg. or higher has been obtained repeatedly. This activity is in the same range as that reported by Potts and Gallagher for the oxytocic material which they prepared (4), which had a potency of 700 units per mg. Since the oxytocic hormone is soluble in 1-butanol and 2-butanol as well as in water, it is possible to distribute it between one of these alcohols and an aqueous solution. The partition coefficients of the oxytocic material between 2-butanol and various aqueous solutions were determined, and, from the solvent pairs tested, two were selected for use in the purification