Grupo de Ecotoxicología, Laboratorio de Ecofisiología, Universidad Nacional Autónoma de México, Ciudad Universitaria, C.P. 04510 Mexico D.F., Mexico.
Aquat Toxicol. 2011 Oct;105(3-4):728-34. doi: 10.1016/j.aquatox.2011.09.001. Epub 2011 Sep 14.
The axolotl Ambystoma mexicanum is a neotenic salamander considered a good biological model due to its ability to regenerate limbs, tail, brain and heart cells. Nevertheless, severe reduction of A. mexicanum wild populations in the lacustrine area of Xochimilco, the natural habitat of the axolotl, could be related to several environmental pressures as the presence of organophosphate pesticides (OPPs), intensively applied in agricultural activities in Xochimilco. Thus the aim of this study was to evaluate the effect of environmentally realistic chlorpyrifos (CPF) concentrations, a OPP commonly used in this zone, on esterases activity (acetylcholinesterase and carboxylesterase) and bioconcentration of CPF and to relate them with the motor activity of A. mexicanum juveniles. Axolotls were exposed 48 h to 0.05 and 0.1mg CPF/L, and the responses were evaluated at the end of the CPF exposure. Results suggest that CPF is bioconcentrated into axolotls and that the CPF internal concentrations are related with the observed inhibition activity of AChE (>50%) and CbE (≈ 50%). CPF concentration responsible of the inhibition of the 50% of AChE activity (IC50) was estimated in 0.04 mg CPF/L; however IC50 for CbE activity was not possible to calculate since inhibition levels were lower than 50%, results that suggest a higher resistance of CbE enzymatic activity to CPF. However, motor activity was a more sensitive endpoint to CPF poisoning since time that axolotls spent active and walking, frequency and speed of swimming, frequency of prey attack were reduced >90% of control groups. The motor activity alterations in the axolotl could be related with the registered esterases inhibition. Thus important alterations on axolotls were identified even at short time and low concentrations of CPF exposure. Also, it was possible to link biochemical responses as esterases activity with higher levels of biological organization as behavior. This study provides tools for the regulation of the use of organophosphorus pesticides in the natural habitat of the axolotl.
墨西哥钝口螈（Ambystoma mexicanum）是一种具有幼态持续特性的蝾螈，因其具有再生四肢、尾巴、大脑和心脏细胞的能力而被认为是一种良好的生物模型。然而，在墨西哥城湖泊地区（即墨西哥钝口螈的自然栖息地），墨西哥钝口螈野生种群的严重减少可能与多种环境压力有关，如有机磷农药（OPPs）的存在，这些农药在墨西哥城的农业活动中被大量使用。因此，本研究旨在评估环境相关浓度的毒死蜱（CPF）对酯酶活性（乙酰胆碱酯酶和羧酸酯酶）的影响，并对 CPF 的生物浓缩作用进行评价，同时将其与墨西哥钝口螈幼体的运动活性相关联。墨西哥钝口螈在 0.05 和 0.1mg CPF/L 的浓度下暴露 48 小时，并在 CPF 暴露结束时评估其反应。结果表明，CPF 可被墨西哥钝口螈生物浓缩，并且 CPF 的内部浓度与观察到的 AChE 抑制活性（>50%）和 CbE 抑制活性（≈50%）有关。CPF 浓度抑制 50%的 AChE 活性（IC50）估计为 0.04mg CPF/L；然而，由于抑制水平低于 50%，因此无法计算 CbE 活性的 IC50，这表明 CbE 酶活性对 CPF 的抵抗力更高。然而，运动活性是对 CPF 中毒更敏感的终点，因为活跃和行走的时间、游泳的频率和速度、捕食猎物的频率减少了>对照组的 90%。墨西哥钝口螈的运动活性改变可能与所记录的酯酶抑制有关。因此，即使在短时间和低 CPF 暴露浓度下，也能识别出对墨西哥钝口螈的重要改变。此外，还可以将生化反应（如酯酶活性）与更高水平的生物组织（如行为）联系起来。本研究为有机磷农药在墨西哥钝口螈自然栖息地的使用提供了监管工具。
