A NEW DERIVATIVE OF TRIPHENYLETHYLENE: EFFECT ON IMPLANTATION AND MODE OF ACTION IN RATS

I.C.I. 46,474, the trans-isomer of 1-(p-\g=b\-dimethylaminoeth\x=req-\ oxyphenyl-1,2-diphenylbut-1-ene, is very effective in terminating early pregnancy by preventing implantation when given during the first 4 days after insemination to female rats. In this species, the compound is weakly and atypically oestrogenic and is also anti-oestrogenic, as indicated by its inhibitory effect on the response to exogenous oestrogens of the vaginal epithelium (cornification) and uterus (weight-increase). It is suggested that it can prevent implantation in rats by virtue of its anti-oestrogenic activity, i.e. by counteracting the oestrogen-release from the ovaries which is believed to occur on the 4th day and upon which implantation appears to depend. The corresponding cis-isomer (I.C.I. 47,699) is very different in its properties and behaves in all respects like a conventional oestrogen (orally active\p=m-\e.g.dienoestrol). In rats it is very much more potent as