Biological and Chromatographic Evidence for the Storage of Ethynylestradiol-3-Cyclopentyl Ether in Rat Brain

Abstract

Summary The possible storage of estrogenic substances in brains of rats treated with ethynylestradiol (EE) or its 3-cyclopentyl ether (EECPE) was investigated. Twenty-four or 72 hours after a single oral administration of 2 mg of the test steroids, brains were removed and extracted with methylene chloride. The extracts were bio-assayed for uterotrophic potency or subjected to thin layer chromatography. Uterotrophic activity, corresponding to 2.3 and 0.5 μg of the standard, was detected 24 and 72 hours after administration of EECPE. This material corresponded to authentic EECPE in two TLC systems. Similar chromatographic analyses showed that the estrogenic substance, previously detected biologically in body fat of rats treated with EECPE(1), likewise corresponded to the unaltered ether. Neither bioassay nor TLC detected any estrogenic substances in brains or fat of rats treated with EE. The evidence supports the view that EECPE, but not EE, is stored unaltered in brain and body fat and that such storage may account for the enhanced anti-gonadotrophic and uterotrophic potency of the etherified form of the steroid.