title: All ZZ male Xenopus laevis provides a clear sex-reversal test for feminizing endocrine disruptors.
abstract: We investigated the possibility of using all ZZ male Xenopus laevis tadpoles produced by mating normal ZZ males with feminized ZZ males to detect estrogenic chemical activity. We examined the effects of 17beta-estradiol (E2) on sex differentiation by treating NF stage 49/50 to stage 57 tadpoles with 0.1, 1, 10, and 20 nM E2 for 4 weeks. Following this, the tadpoles were allowed to develop in clean water until the animals reached stage 66. Increased developmental abnormalities and mortality were not observed in all E2-exposed groups during metamorphosis. Feminization of gonads was detected at all E2 concentrations, whereas nonexposed controls developed testes. Morphological and histological analyses showed that feminized gonads were ovaries. Five and one hermaphroditic frogs were found in the 0.1 and 1 nM E2 groups, respectively, showing testicular as well as ovarian regions within one gonad. These results indicate that phenotypically normal females can be produced from genetic males and demonstrate the utility of a sex-reversal test based on all ZZ males for examining in vivo effects of chemicals with estrogenic activity. The testing of all ZZ male tadpoles might be a useful tool for assessment of feminizing compounds not only estrogenic substance.
authors.affiliation: Biotechnology Research Laboratory, Towa Kagaku Co., Ltd., 3-13-26 Kagamiyama, Higashihiroshima-shi, Hiroshima 739-0046, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Oka
authors.forename: Naoko
authors.initials: N
authors.lastname: Mitsui
authors.forename: Megumi
authors.initials: M
authors.lastname: Hinago
authors.forename: Maki
authors.initials: M
authors.lastname: Miyahara
authors.forename: Takaaki
authors.initials: T
authors.lastname: Fujii
authors.forename: Osamu
authors.initials: O
authors.lastname: Tooi
authors.forename: Noriaki
authors.initials: N
authors.lastname: Santo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Urushitani
authors.forename: Taisen
authors.initials: T
authors.lastname: Iguchi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Hanaoka
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Mikamid
mesh_terms: D000818:Animals; D012734:Disorders of Sex Development; D052244:Endocrine Disruptors / Q000633:toxicity*; D004958:Estradiol / Q000633:toxicity*; D005260:Female; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008297:Male; D010053:Ovary / Q000033:anatomy & histology / Q000187:drug effects; D012733:Sex Differentiation / Q000187:drug effects; D013737:Testis / Q000033:anatomy & histology / Q000187:drug effects; D018675:Toxicity Tests / Q000379:methods; D014982:Xenopus laevis / Q000254:growth & development*
chemical_list: D052244:Endocrine Disruptors; D004958:Estradiol