Assessment using hydra of endocrine disruptors contaminated in freshwater environment

研究了双酚A（BPA）对淡水环境中进化上原始的无脊椎动物寡聚水螅（Hydra oligactis）无性生殖和有性生殖的影响。水螅在20℃下饲养培养时，能连续产生芽（无性繁殖）。当水螅在低温（10℃）下饥饿时，它开始产生性腺（有性生殖）而不是芽。在有性生殖条件下，向雄性或雌性水螅给予0.5-4 ppm BPA，不仅对睾丸形成有选择性的不良影响（由于化合物的雌激素性质，预期会产生不同的影响），而且对睾丸和卵形成都有不良影响。在无性繁殖条件下，0.5-1 ppm BPA对芽的萌发有促进作用，2-3 ppm BPA对芽的萌发有抑制作用。将雄性水螅置于10℃下继续取食，既产生芽又产生精巢。有趣的是，在10℃下对出芽的刺激和不利影响所需的BPA剂量低于20℃。这一事实表明，在较低的温度下，更多的BPA在水螅中积累，这被证明是正确的与放射性标记的BPA。我们在这里表明，在0.5-1 ppm BPA刺激出芽的条件下，即使在低温下也会抑制睾丸的形成。干细胞增殖和分化为性腺细胞之间的平衡似乎是出芽或睾丸形成的决定性因素。这些事实表明，BPA在相对较高的剂量影响水螅的有性和无性生殖可能通过影响干细胞的增殖和定向干细胞分化为生殖细胞。

The effects of bisphenol A (BPA), an estrogenic compound, on asexual and sexual reproduction were examined in an evolutionarily primitive invertebrate, Hydra oligactis, living in freshwater environment. When hydra was fed and cultured at 20℃, it continuously produced buds (asexual reproduction). When hydra exposed to low temperature (10℃) was starved, it started to produce gonads (sexual reproduction) in stead of buds. BPA at 0.5-4 ppm given to male or female hydra under the condition for sexual reproduction had the adverse effects not selectively on testis formation (differential effects were expected because of estrogenic nature of the compound) but both on testis and egg formation. On the other hand, BPA at 0.5-1 ppm had stimulatory whereas that at 2-3 ppm had suppressive effects on the budding under the condition for asexual reproduction. When male hydra placed at 10℃ was continued to feed, it produced buds as well as testes. Interestingly, doses of BPA required for stimulatory and adverse effects on budding were lower at 10℃ than at 20℃. The fact suggested more accumulation of BPA in hydra at lower temperature, which is proven correct with radio-labeled BPA, It is known that processes involved in testis differentiation are sensitive to high temperature. We showed here that the condition under which budding was stimulated by BPA at 0.5-1 ppm, caused suppression of testis formation even at low temperature. Balance between proliferation of stem cells and differentiation into gonad cells seems to be decisive of budding or testis formation. All these facts suggest that BPA at relatively high doses affect sexual and asexual reproduction of hydra maybe via effects on proliferation of stem cells and differentiation of committed stem cells into germ cells.