除草剂乙草胺对非洲爪蟾性腺发育的影响

使用性腺发育对内分泌干扰作用敏感的两栖动物非洲爪蟾作为模型动物,通过考察性别比、性腺整体形态和组织学形态来揭示乙草胺对其性腺发育的影响,从而确定乙草胺是否具有内分泌干扰活性.46/47期蝌蚪经不同浓度(5μg·L-1、10μg·L-1、20μg·L-1)的乙草胺暴露处理至变态后1个月,在变态结束后3个月时,解剖性腺、鉴别雌雄并固定性腺做组织切片.实验中对照组所有性腺都为典型的卵巢或睾丸,雌性百分率为48.78%(20/41).而乙草胺暴露组却出现了明显的异常睾丸,其总体上是睾丸,但又带有部分卵巢的特征,在统计性别时将具有异常睾丸的爪蟾归为雄性.5μg·L-1、10μg·L-1、20μg·L-1暴露组的雌性百分率分别为:57.14%(24/42)、66.67%(22/36)、55.26%(21/38).虽经统计分析无显著性差异,但乙草胺暴露组中雌性多于雄性的趋势和出现带有雌性特征的雄性的现象,一定程度上却暗示了乙草胺可能对非洲爪蟾的性腺发育有雌性化作用.正常睾丸的组织学结构应有发育成熟的生精小管,其内有各个时期的精子囊和生精细胞及精子.但经乙草胺处理的爪蟾睾丸却表现出几种明显的异常:没有生精小管,相反却像发育早期的睾丸一样,充满大量的精原细胞,完全没有生精细胞和精子;有生精小管结构,但其内精子囊结构不明显,生精细胞少并且排列混乱,其间有很大的空隙;睾丸出现腔隙,并有大量体细胞存在,这种结构与57期的卵巢相似;睾丸中出现异常的生精细胞,与58期卵巢的卵细胞相似;睾丸组织中有明显的卵细胞散布.组织学研究发现的乙草胺导致的睾丸结构证明了乙草胺对非洲爪蟾的睾丸发育有抑制雄性化作用和雌性化作用,即乙草胺对非洲爪蟾的性腺发育有内分泌干扰作用.

Effects of Herbicide Acetochlor on the Gonadal Development of Xenopus laevis

The aim of the study: Using Xenopus laevis as a common model animal to distinguish if acetochlor is endocrine disruptor according to the effects of acetochlor on the gonadal development of Xenopus laevis. Xenopus laevis tadpoles(stage 56) were exposed to a serial concentration of acetochlor (5μg·L-1,10μg·L-1,20μg·L-1). Three month later,the effects of acetochlor on the gonadal development of Xenopus laevis was in evidence by the percentage of sexes and photomicrographs of gonadal sections. Female percentages based on gonadal examination using microscope in the control group and groups exposed to acetochlor is 48.78%(20/41),57.14% (24/42,5μg·L-1);66.67%(22/36,10μg·L-1);55.26% (21/38,20μg·L-1). The trend(female>male) and the male with female character suggest that acetochlor induces feminization in Xenopus laevis. Normal testicular tissue exhibits compact structure with seminiferous tubes,spermatocyst and spermatozoa. Some testicular tissue of frogs exposed to acetochlor is immature and exhibits looser structure with fewer seminiferous tubes,spermatocyst,and spermatozoa. Some testicular tissue exhibits a lot of somatic cells and lacuna,which is similar to the normal ovarian tissue at stage 57. Some testicular tissue exhibits a lot of abnormal cells,which is similar to the cells of normal ovarian tissue at stage 58. Some testicular tissue consists of ovarian tissue and testicular tissue. Photomicrographs of gonadal sections confirm that acetochlor disturb the gonadal development of Xenopus laevis.