An in vitro demonstration of oestrogenicity with potential for exploitation as a quantitative assay for oestrogenic potency.

The pre-implantation embryo of the mouse undergoes a histochemically detectable change in the properties of its trophoblastic cell-surface coat in the immediate pre-implantation period. This change is oestrogen-dependent in vivo and can be induced in vitro in a concentration-dependent manner by oestradiol-17 beta. There is evidence that this coat change is of functional importance in the process of implantation, and its demonstration is of potential value as the basis of an in vitro assay of oestrogenicity.