A BIOLOGIC ASSAY OF "INTERNATIONAL STANDARD" ESTRIN AND OF CERTAIN COMMERCIAL PREPARATIONS

¹ Research Laboratories, University of Denver

A thorough biologic assay was made of International Standard Estrin. It was found that the rat unit, i.e., the amount necessary to produce a positive reaction in 50 per cent of a large group of spayed rats, was as follows: Single injection in oil, 1.3 gamma; multiple injection in oil, 1.5 gamma; single injection, aqueous, 3.8 gamma; multiple injection, aqueous, 0.74 gamma; multiple injection, emulsion, 0.76 gamma.

An assay of certain commercial estrogenic preparations indicated, for oil solutions, that the biologic activity, per International Unit stated by the label to be present, corresponded with the activity of the International Standard. For aqueous preparations, the biologic activity, per International Unit stated by the label to be present was only one-sixth to one-seventh as great as the biologic activity per International Unit of the International Standard material.