All ZZ male Xenopus laevis provides a clear sex-reversal test for feminizing endocrine disruptors.
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.
Oka
Tomohiro
T
Biotechnology Research Laboratory, Towa Kagaku Co., Ltd., 3-13-26 Kagamiyama, Higashihiroshima-shi, Hiroshima 739-0046, Japan.
Mitsui
Naoko
N
Hinago
Megumi
M
Miyahara
Maki
M
Fujii
Takaaki
T
Tooi
Osamu
O
Santo
Noriaki
N
Urushitani
Hiroshi
H
Iguchi
Taisen
T
Hanaoka
Yoichi
Y
Mikamid
Hirokazu
H
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*
D052244:Endocrine Disruptors; D004958:Estradiol