Acclimation to low level exposure of copper in Bufo arenarum embryos: linkage of effects to tissue residues.

Cristina Pérez-Coll,Jorge Herkovits

doi:10.3390/ijerph2007040012

Abstract

The acclimation possibilities to copper in Bufo arenarum embryos was evaluated by means of three different low level copper exposure conditions during 14 days. By the end of the acclimation period the copper content in control embryos was 1.04 +/- 0.09 microg g(-1) (wet weight) while in all the acclimated embryos a reduction of about 25% of copper was found. Thus copper content could be considered as a biomarker of low level exposure conditions. Batches of 10 embryos (by triplicate) from each acclimation condition were challenged with three different toxic concentrations of copper. As a general pattern, the acclimation protocol to copper exerted a transient beneficial effect on the survival of the Bufo arenarum embryos. The acclimation phenomenon could be related to the selection of pollution tolerant organisms within an adaptive process and therefore the persistence of information within an ecological system following a toxicological stressor.

Highlights

Most toxicity studies focus on lethal or sublethal effects, from an environmental point of view, low level concentrations are probably the most frequent background exposure scenarios
A reduction of approximately 25% of copper was found in the embryos treated with low copper concentrations respect to the copper content in control embryos (1.04 ± 0.09 μg Cu.g-1 wet weigh)
In unpolluted freshwater bodies the copper contents are in the range of 1-20μg.L-1 [8], it is noteworthy that within these concentrations significant toxic effects were reported in diatoms and some invertebrates, notably cladocerans

Summary

Introduction

Most toxicity studies focus on lethal or sublethal effects, from an environmental point of view, low level concentrations are probably the most frequent background exposure scenarios. It is well known that some low level exposure to specific harmful physical or chemical agents may exert a beneficial effect on certain parameters such as longevity, cell division rate, regeneration processes [1] and an enhanced resistance to subsequent challenge to the same environmental agent at toxic doses/concentrations [2, 3] In the case of low level exposure, within two orders of magnitude below the noobservable-effect-level (NOEL) values, the Arndt-Schulz law predicts the obtaining of a dose-response β curve with a low dose stimulation-high dose inhibition effect referred sometimes as hormesis [4]. Its essentiality arises from its specific incorporation into a large number of proteins for catalytic and structural purposes. In unpolluted freshwater bodies, the copper contents are in the range of 1-20μg.L-1 [8] it was reported that copper concentrations as low as 1-2 μg /L could exert adverse

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