全氟辛磺酸(PFOS)对非洲爪蟾(Xenopus laevis)生长发育、甲状腺和性腺组织学的影响

Effects of Perfluorooctanesulfonate on the Growth, Metamorphosis, Thyroid and Gonadal Histology of Xenopus laevis

为了揭示全氟辛磺酸(PFOS)的甲状腺激素和性激素干扰效应,并探索运用爪蟾动物模型同时检测多种环境内分泌干扰效应的可能性,将NF48阶段非洲爪蟾(Xenopus laevis)蝌蚪暴露于0.01、0.1和1mg·L-1PFOS中6个月,检测PFOS对爪蟾生长、变态、甲状腺和性腺的影响.结果表明,在各取样时间,PFOS组爪蟾体长、体重和蝌蚪尾长与对照组均无显著差异(p>0.05);2个月后,PFOS组比对照组平均慢1个发育阶段,4和6个月后,0.01mg·L-1PFOS组反而比对照组分别快1和2个发育阶段.6个月后,PFOS组甲状腺出现滤泡上皮细胞增生、胶质减少甚至空泡化等现象,且随着PFOS浓度的增加而加重;各组幼蛙性腺出现间性、睾丸珍珠状和先天性萎缩等畸形现象,外观为间性的性腺主要表现为睾丸组织中产生类似雌性个体的卵巢腔.对照组幼蛙的雌雄比为0.5:1,而暴露组分别为2.3:1(0.01mg·L-1组)、4.5:1(0.1mg·L-1组)和5:1(1mg·L-1组).上述结果表明,PFOS对爪蟾的变态过程具有小剂量刺激效应,能引起甲状腺组织结构的损伤,导致睾丸组织的雌性化和雌雄性比的异常升高,表现出明显的甲状腺激素和性激素干扰效应,可以认定为一种环境内分泌干扰物.实验同时表明非洲爪蟾可以用于多种环境内分泌干扰效应的同时检测.

To reveal thyroid hormones and sex hormones disrupting effects of perfluorooctanesulfonate（PFOS） and to discuss the possibility to screen both endocrine effects using model animal Xenopus laevis in the same experiment, X. laevis tadpoles（NF48） were exposed to PFOS at the concentrations of 0.01, 0.1 and 1mg·L^-1 for 6 months. The changes of growth, metamorphosis, thyroid gland and gonad of X. laevis were measured. Compared with the control, the body length, body weight and tadpole tail length did not show significant changes in PFOS treatment groups（p〉0.05）. After 2-month exposure, the developmental stage of treatment groups was 1 stage slower than that of control group, however, 0.01mg·L^-1 treatment group showed 1 and 2 stages faster than those of control group after 4 and 6 months exposure, respectively. PFOS induced thyroid follicle cell hyperplasia, the depletion of colloid and even vacuolation with dose-effect relationships after 6 months exposure. Malformations of gonad with intersex, pearling and segmental aplasia were found in all treatment groups. The gonad with intersex showed a testis tissue with a female ovarian cavity like structure. The sex ratio （female/male） of control group was 0.5：1,while they were 2.3：1（0.01mg·L^-1 group）, 4.5：1（0.1mg·L^-1 group） and 5：1（1mg·L^-1 group） in treatment groups. These results showed that PFOS could stimulate the metamorphosis of tadpoles at low dose, induce the damage of thyroid histology, and lead to the feminization of testis histology and the abnormal elevation of sex ratio（female/male）. In brief, PFOS had significant thyroid hormone and sex hormone disrupting effects and could be regarded as one of endocrine disrupting chemicals. Additionally, these results suggested that X. laevis could be used as the model animal to test simultaneously a variety of endocrine disrupting effects.