SGER: Characterization of Hermaphroditism in Rana Pipiens

之前的实验室研究表明，除草剂阿特拉津会导致非洲爪蛙(Xenopus Laevis)和美国豹蛙(Rana Piiens)出现性异常。两性畸形(既有睾丸又有卵巢的动物或有发育中卵子的睾丸)是观察到的最严重的异常。后来的研究表明，在野外通过农业径流接触阿特拉津的人群中也发现了类似的异常。虽然因果假说得到了实验室数据的支持，但两性现象可能是自然发生的，与野外阿特拉津污染的相关性可能是巧合的。目前的研究将从两个方面探讨这种可能性：1)将在实验室饲养来自野生种群的两性动物，以确定在没有接触阿特拉津污染的水的情况下是否会发生两性畸形。来自这些种群的动物的发育将与来自野生环境中未表现出雌雄同体的种群的动物进行比较。2)在野外没有雌雄同体的种群的动物将被饲养在从野外观察到的雌雄同体的地区收集的阿特拉津污染的水中，以确定它是否会在通常不表现出这种发育模式的动物中诱导雌雄同体。上面概述的两个目标将确定两性异体是自然发生的，还是污染物暴露的结果。这些研究很重要，原因如下：1)阿特拉津是地下水和饮用水中最常见的污染物；2)实验室研究表明，阿特拉津的活性水平低至百万分之0.1，即使在雨水中也能超过这个水平；3)阿特拉津和其他杀虫剂可能与两栖类动物的衰退有关；4)已证实阿特拉津影响两栖动物的内分泌机制已在鱼类、爬行动物和哺乳动物中得到证实；5)阿特拉津可能导致老鼠患上癌症，而在职业暴露于阿特拉津的人类(乳腺癌和前列腺癌)中观察到同样的机制。

Previous laboratory studies showed that the herbicide, atrazine, induced sexual abnormalities in both African clawed frogs (Xenopus laevis) and American leopard frogs (Rana pipiens). Hermaphroditism (animals with both testes and ovaries or testes with developing eggs) was the most severe abnormality observed. Later studies showed that similar abnormalities were found in the wild in populations exposed to atrazine via agricultural runoff. Although the cause-effect hypothesis is supported by laboratory data, it is possible that hermaphroditism occurs naturally and that the correlation with atrazine contamination in the wild may be coincidental. The current study will address the possibility in two ways: 1) Animals from populations in the wild that show hermaphroditism will be reared in the laboratory to determine if hermaphroditism occurs in the absence of exposure to atrazine-contaminated water. Development of animals from these populations will be compared with animals from populations that do not show hermaphroditism in the wild. 2) Animals from populations that do not show hermaphroditism in the wild will be reared in atrazine-contaminated water collected from areas where hermaphroditism was observed in the wild to determine if it will induce hermaphroditism in animals that do not normally show this developmental pattern.The two aims outlined above will determine if hermaphroditism occurs naturally, or is the result of contaminant exposure. These studies are important for several reasons: 1) atrazine is the most common contaminant in ground and drinking water; 2) laboratory studies showed that atrazine is active at levels as low as 0.1 parts per billion, a level that can be exceeded even in rain water; 3) atrazine and other pesticides may be involved in amphibian declines; 4) the proposed endocrine mechanisms by which atrazine affects amphibians have been documented in fish, reptiles, and mammals; 5) the same mechanisms may be responsible for cancers produced in rats by atrazine and observed in humans occupationally exposed to atrazine (breast and prostate cancer).