Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), Québec, Canada.
Environ Toxicol Chem. 2014 Jun;33(6):1372-9. doi: 10.1002/etc.2565.
The effects of pH on metal uptake and toxicity in aquatic organisms are currently poorly understood and remain an evolving topic in studies about the biotic ligand model (BLM). In the present study, the authors investigated how pH may influence long-term (4 d) uranium (U) accumulation and chronic toxicity in batch cultures of the freshwater green alga Chlamydomonas reinhardtii. The toxicity expressed as a function of the free uranyl ion was much greater at pH 7 (effective concentration, 50% [EC50] = 1.8 × 10(-9) M UO2 (2+) ) than at pH 5 (EC50 = 1.2 × 10(-7) M UO2 (2+) ). The net accumulation rate of U in algal cells was much higher at pH 7 than at pH 5 for the same free [UO2 (2+) ], but the cells exposed at pH 5 were also more sensitive to intracellular U than the cells at pH 7 with EC50s of 4.0 × 10(-15) and 7.1 × 10(-13) mol of internalized U cell(-1) , respectively. The higher cellular sensitivity to U at pH 5 than at pH 7 could be explained partly by the increase in cytosolic U binding to algal soluble proteins or enzymes at pH 5 as observed by subcellular fractionation. To predict U accumulation and toxicity in algae accurately, the important modulating effects of pH on U accumulation and U cellular sensitivity should be considered in the BLM.
目前，人们对 pH 值对水生生物金属吸收和毒性的影响知之甚少，这仍然是生物配体模型 (BLM) 研究中一个不断发展的课题。在本研究中，作者研究了 pH 值如何影响淡水绿藻莱茵衣藻的长期（4 天）铀（U）积累和慢性毒性。作为游离铀离子函数的毒性在 pH 值为 7 时（有效浓度，50%[EC50] = 1.8×10(-9) M UO2 (2+) ）比在 pH 值为 5 时（EC50 = 1.2×10(-7) M UO2 (2+) ）大得多。对于相同的游离[UO2 (2+) ]，U 在藻类细胞中的净积累速率在 pH 值为 7 时比在 pH 值为 5 时高得多，但在 pH 值为 5 时暴露的细胞对细胞内 U 比在 pH 值为 7 时的细胞更敏感，EC50 分别为 4.0×10(-15)和 7.1×10(-13) mol 内化 U 细胞(-1) 。在 pH 值为 5 时，细胞对 U 的敏感性高于 pH 值为 7 时，这可以部分解释为细胞溶质 U 与藻类可溶性蛋白质或酶的结合增加，这是通过亚细胞分级分离观察到的。为了准确预测藻类中的 U 积累和毒性，BLM 中应考虑 pH 值对 U 积累和 U 细胞敏感性的重要调节作用。
