Hartnik Thomas, Styrishave Bjarne
Bioforsk, Norwegian Institute for Agricultural and Environmental Research, Soil and Environment Section, As, Norway.
J Agric Food Chem. 2008 Nov 26;56(22):11057-64. doi: 10.1021/jf8017904.
Knowledge about the bioavailability and metabolism of pesticides in soil organisms facilitates interpretation of its toxicity in soil. The present study relates uptake kinetics and metabolism of two insecticides, the pyrethroid alpha-cypermethrin (alpha-CYP) and the organophosphate chlorfenvinphos (CFVP), in the earthworm Eisenia fetida to their lethal and sublethal toxicity. Experiments were conducted in two soils with different organic matter contents to provide media with contrasting sorption capacity for the insecticides. The results showed that organophosphate CFVP was, when taken up by earthworms, rapidly and irreversibly bound to biomolecules and the fraction of extractable parent insecticide and metabolites was low. In contrast, alpha-CYP was rapidly metabolized by earthworms but did not form conjugates. It seems that the phase II metabolism of alpha-CYP is inhibited in earthworms, resulting in an increasing accumulation of its metabolites. Instantaneous binding of non-altered CFVP to the target site presumably resulted in a higher toxicity compared to alpha-CYP and explains the small difference between lethal and reproduction toxicity. For alpha-CYP, however, accumulation of alpha-CYP metabolites in earthworms during chronic exposure may explain the large observed difference between lethal and sublethal toxicity. Bioaccumulation and toxicity of either insecticide decreased with increasing organic matter content in soil, emphasizing the role of compound sorption on bioavailability and toxicity for soil organisms.
了解农药在土壤生物中的生物利用度和代谢情况有助于解释其在土壤中的毒性。本研究将蚯蚓 Eisenia fetida 对两种杀虫剂（拟除虫菊酯α-氯氰菊酯（α-CYP）和有机磷毒死蜱（CFVP））的吸收动力学和代谢与其致死和亚致死毒性联系起来。在两种不同有机质含量的土壤中进行实验，以提供对杀虫剂具有不同吸附能力的介质。结果表明，有机磷 CFVP 被蚯蚓摄取后，会迅速且不可逆地与生物分子结合，可提取的母体杀虫剂和代谢物的比例较低。相比之下，α-CYP 被蚯蚓迅速代谢，但不会形成结合物。似乎蚯蚓体内α-CYP 的Ⅱ相代谢受到抑制，导致其代谢物积累增加。未改变的 CFVP 与靶位点的瞬时结合可能导致其毒性高于α-CYP，并解释了致死毒性和生殖毒性之间的微小差异。然而，对于α-CYP 而言，长期暴露期间蚯蚓体内α-CYP 代谢物的积累可能解释了观察到的致死毒性和亚致死毒性之间的巨大差异。两种杀虫剂的生物累积和毒性均随土壤中有机质含量的增加而降低，这突出了化合物吸附对土壤生物的生物利用度和毒性的作用。
