[Estrogen dependance of the progesterone "receptor" in human tissues (author's transl)]

The concentration of specific progesterone receptor (RP) has been measured in the endometrium of 31 normal menstruating women during the two phases of their menstrual cycle, and compared with the plasma oestradiol-17 beta (E2) concentrations. There was no relationship between RP and plasma E2 when the two phases of the cycle were considered, however a correlation was observed when the follicular phase was only considered. The relationship between oestrogen and RP was then more directly studied in a breast cancer cell line in tissue culture (MCF-7). RP induction by E2 as well as oestriol was demonstrated, but oestrone was ineffective.