Some Activities of a Potent Steroidal Antiestrogen

The biological activity of estr-4- ene-3-one-spiro-17α-2'-(tetrahydrofuran) was investigated in mice and rabbits. In mice the compound was weakly uterotropic, while at the same time the carbonic anhydrase (CA) activity of the uteri was depressed. In the antiestrogenic assay the compound exhibited very pronounced activity. The estrogen-stimulated CA activity was inhibited to a greater extent than the uterine weight. Testosterone-stimulated uterine weight increase was not antagonized by the compound, whereas the CA activity was depressed. In immature rabbits the compound exhibited progestational activity when it was administered by itself. In combination with progesterone, especially at high dosages, furanestrenone was antiprogestational as judged by the decrease in endometrial CA activity. (Endocrinology 79:125, 1966)