THE PREPARATION OF PROLACTIN

¹ From the Carnegie Institution of Washington, Station for Experimental Evolution, Cold Spring Harbor, New York

A procedure for extraction and proximate purification of prolactin is fully described. The tissue is first extracted with 60 to 70 per cent aqueous ethanol at pH 9 to 10, and this followed by complete precipitation of the active principles at a higher ethanol concentration and at pH 6.0. The prolactin is next separated from the bulk of follicle-stimulating and thyreotropic hormones by taking advantage of the insolubility of prolactin between pH 3 to 4 in the presence of sulphates. The hormone is further purified through use of its solubility in aqueous ethanol. About 70 per cent of the prolactin present in the original tissue is thus obtained in one fraction uncontaminated by F. S. H. and thyreotropic hormone. At pH 8.0 prolactin can be heated to boiling for one hour or to 60°C. for five hours without great loss of potency.