Venturino Andrés, Rosenbaum Enrique, Caballero de Castro Adriana, Anguiano Olga Liliana, Gauna Lidia, Fonovich de Schroeder Teresa, Pechen de D'Angelo Ana María
Cátedra de Química Biológica, Facultad de Ciencias Agrarias, Universidad Nacional del Comahue, Buenos Aires 1400-8300 Neuquén, Argentina.
Biomarkers. 2003 May-Aug;8(3-4):167-86. doi: 10.1080/1354700031000120116.
Amphibians are good bioindicators of environmental pollution due to their susceptibility to chemicals during their freshwater cycles. The effects of environmental pollution, together with changes in human activity and climate, have contributed to the reduction in the amphibian population over recent decades. However, toxicological research on amphibians has been rather scarce compared with that on other vertebrates. In this article we review the biochemical alterations underlying xenobiotic action and/or the detoxifying responses described for anuran species, with the aim of establishing possible biomarkers of effect. During the embryonic development of anurans, morphological and behavioural alterations are the effects most frequently cited in connection with chemical exposures. However, such biomarkers have a low sensitivity and are unspecific compared with biochemical alterations. Some primary pesticide targets, in particular cholinesterases for organophosphates and carbamates, have been evaluated. Esterases change seasonally and with the stage of development, and their sensitivity to anticholinesterase agents varies between species. Thus their use as biomarkers in anurans must be carefully analysed. Enzymes and endogenous compounds related to oxidative metabolism may also be used as biomarkers of effect. Glutathione pool, glutathione-S-transferases and metallothioneins respond in different ways to pesticides and heavy metals in anuran embryos and tadpoles. Mixed-function oxidases, in turn, are less developed in amphibians, and show a reduced induction in response to pesticide exposures. Endogenous polyamine levels are also proposed as good age-related biomarkers of damage. Finally, molecular biomarkers related to receptor binding, signal transduction and genetic response have gained increasing relevance, as they have been implicated in the fertilisation process and the earliest events in anuran development. The identification of transcription factors associated with the exposure of amphibians to xenobiotics as well as other alterations in hormone signalling appears highly promising. However, these techniques are likely to complement other methods. In conclusion, the use of several biomarkers with multiple endpoints is needed to link exposure to response and to provide better predictive tools for the environmental protection of endangered anuran species.
两栖动物是环境污染的良好生物指示物种，因为它们在淡水生活周期中对化学物质敏感。近几十年来，环境污染的影响，加上人类活动和气候的变化，导致两栖动物数量减少。然而，与其他脊椎动物相比，对两栖动物的毒理学研究相当匮乏。在本文中，我们综述了无尾两栖类物种对外源化合物作用和/或解毒反应的生化改变，目的是确定可能的效应生物标志物。在无尾两栖类胚胎发育过程中，形态和行为改变是与化学物质暴露相关最常被提及的效应。然而，与生化改变相比，这些生物标志物敏感性较低且不具特异性。一些主要的农药作用靶点，特别是有机磷和氨基甲酸酯类农药的作用靶点胆碱酯酶，已得到评估。酯酶会随季节和发育阶段变化，且它们对抗胆碱酯酶剂的敏感性因物种而异。因此，在无尾两栖类中使用它们作为生物标志物必须谨慎分析。与氧化代谢相关的酶和内源性化合物也可作为效应生物标志物。谷胱甘肽池、谷胱甘肽-S-转移酶和金属硫蛋白在无尾两栖类胚胎和蝌蚪中对农药和重金属有不同的反应方式。另一方面，混合功能氧化酶在两栖动物中发育程度较低，对农药暴露的诱导反应减弱。内源性多胺水平也被认为是与损伤相关的良好年龄生物标志物。最后，与受体结合、信号转导和基因反应相关的分子生物标志物越来越受到关注，因为它们与受精过程和无尾两栖类发育的早期事件有关。鉴定与两栖动物接触外源化合物以及激素信号传导的其他改变相关的转录因子似乎很有前景。然而，这些技术可能会补充其他方法。总之，需要使用具有多个终点的多种生物标志物来将暴露与反应联系起来，并为濒危无尾两栖类物种的环境保护提供更好的预测工具。
