Action of estradiol and tamoxifen on the Müllero-regressive activity of the chick embryonic testis assayed in vivo by organotypic grafting.
In the chick, the implantation of a testis graft from a 13-day-old male donor embryo into the extra-embryonic coelom of 3-day-old female embryos induces the total regression of their Müllerian ducts because of the anti-Müllerian hormone (AMH or MIS) secreted by the implant. Pre-treatment of the donors with estradiol (E2), between day 12 and day 13, counteracts in a significant way the Müllero-regressive activity of the implant. Co-treatment of donors at the same stage with both Tamoxifen (TAM) and E2 restores the initially observed activity, thus demonstrating the presence of Tamoxifen-sensitive estrogen receptors at the late stage of treatment in the Sertoli cells responsible for AMH secretion. The treatment of 3-day-old male donor embryos with E2 causes the differentiation of their left gonad into an ovotestis which provides implants totally devoid of Müllero-regressive activity. The additional treatment with TAM of the grafted host embryos, does not modify the results obtained when E2-treated male gonads are grafted to host embryos not treated with TAM. This shows that the lack of Müllero-regressive activity exhibited by the E2-treated male gonads does not depend on the estrogens they may secrete during the time of the assay, i.e., it cannot be attributed to a protecting action of estrogens on the MDs of the host. Our results therefore favor the idea that E2 down-regulates AMH. The relevance of such a regulation to the phenomenon of Müllerian duct maintenance, either in the E2-feminized male or in the female chick embryo, is discussed.
Faculté de Médecine Paul Broca, Laboratoire d'Histo-Embryologie, Université Bordeaux II, France.
R
R
Stoll
F
F
Ichas
N
N
Faucounau
R
R
Maraud
D000818:Animals; D002642:Chick Embryo / Q000196:embryology* / Q000601:surgery; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005262:Feminization / Q000196:embryology; D008297:Male; D009095:Mullerian Ducts / Q000187:drug effects / Q000196:embryology*; D013629:Tamoxifen / Q000494:pharmacology*; D013737:Testis / Q000187:drug effects / Q000196:embryology* / Q000637:transplantation
D013629:Tamoxifen; D004958:Estradiol