Action of estradiol and tamoxifen on the M�llero-regressive activity of the chick embryonic testis assayed in vivo by organotypic grafting

Abstract

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.

Action of estradiol and tamoxifen on the testis-inducing activity of the chick embryonic testis grafted to the female embryo

“…The comparison of results we recently obtained in vivo (Stoll et al 1993), using small testis grafts, with those we present in this report, provides further support for our previous conclusions concerning the chick embryo. Indeed, a strong correlation exists between the action of E2 on the AMH secretion by the embryonic testis, as revealed in vivo by its action on MDs (Stoll et al 1993), and on the release of the testis-inducing hormone demonstrated in the present work (Table 2).…”

“…In these three batches, the testis grafts recovered from the hosts at the time of fixation present a normal histological structure, without any sign of feminization, as previously shown (Stoll et al 1993). Fig.…”

“…Indeed, a strong correlation exists between the action of E2 on the AMH secretion by the embryonic testis, as revealed in vivo by its action on MDs (Stoll et al 1993), and on the release of the testis-inducing hormone demonstrated in the present work (Table 2). It has been shown that untreated testis grafts induce MD-regressions as well as gonadal masculinization in the female hosts, while an E2-treatment of the grafts inhibits both activities.…”

“…In that respect, it has previously been shown that the period during which these compounds remain active is more than 10 days in the case of TAM, and more than 15 days in the case of E2, under experimental conditions similar to those described (Stoll et al 1993).…”

“…Donor embryos from the third batch were treated with both 300 ~tg of tamoxifen (TAM) in 75 gl of oil at day 10, and 300 gg of E2 (75 pl oil) at day 11. In the fourth batch, donors were treated with 100 gg of E2 (25 gl oil) at day 3, instead of day 11, so that in the male donors the left gonad was differentiating as an ovotestis (Stoll et al 1993).…”