[Effect of tamoxifen on the feminization of chick embryo testis]

The problem was approached whether the feminizing action of oestrogens or androgens on the chick embryo testes could be antagonized by anti-oestrogens or anti-androgens. 100 micrograms of either tamoxifen, cyproterone acetate or compound RU 23908 were injected into the chick embryo after 4 days of incubation and 100 micrograms of either oestradiol benzoate or diethylstilboestrol or 1 mg of either androsterone, dehydroepiandrosterone, 5 alpha-dihydrotestosterone or 5 alpha-androstanedione were given one day later. The surviving embryos were sacrificed when 14-17 days old and their gonads were examined morphologically and in some cases also histologically. Control embryos were only given oestrogens or androgens. Out of 20 surviving embryos treated with oestradiol only, 10 were genetic females and 10 strongly feminized males. After tamoxifen treatment, out of 20 embryos, 11 were females, 7 normal males and 2 slightly feminized males. Thus, tamoxifen suppressed the feminizing action of oestradiol. It antagonized also the feminizing action of diethylstilboestrol. Neither cyproterone acetate nor compound RU 23908 suppressed the feminizing action of androsterone or diethylstilboestrol. But tamoxifen interfered with the androgens, preventing the feminization of the testes. It is suggested that androgens bind to the oestrogen receptor.