Oxidative stress in amphibian embryos exerted by means of physico chemical agents

HERKOVITS J, PÉREZ-COLL CS1, FRIDMAN O1, D´ERAMO JL1 CASTAÑAGA LA1, STOCKERT JC

Baltimore, Maryland

Congreso; XXVI Annual meeting SETAC N. A.; 2005

Setac N. A.

A large number of physico chemical agents such as UV-B irradiation, metals and pesticides produce reactive oxygen species (ROS: singlet oxygen, superoxide and hydroxyl radicals, H2O2) imposed a strong selective pressure which favoured organisms not only able to prevent the adverse effects of oxidative stress, but also to use O2 as the final receptor of electrons in the respiratory chain. ROS are produced physiologically and they participate in metabolic signalling pathways that regulate cell survival, proliferation and apoptosis. However, they are also generated by a large number of xenobiotics and toxic agents. This “good/bad” balance of ROS is highly relevant for living organisms, and it is often surpassed by external conditions that induce oxidative stress, resulting in damage and death.  The adverse effects of oxidative stress on Bufo arenarum embryos at stage 25 (complete operculum) were studied using a wide spectrum of chemical compounds and physical agents. In this work, we describe different experimental conditions that show the possibility (i) to prevent, or at least, to mitigate the adverse effects of oxidative stress, and (ii) to exacerbate the toxicity by means of the synergic effect of agents inducing oxidative stress. In the first case, the photodynamic treatment (generation of ROS in the presence of a photosensitizer, O2 and visible light) exerting lethal effects on the embryos were prevented by previous incubation of the animals with well-known antioxidants (glutathione, ascorbic acid; 1 mM for 48 h). Likewise, the lethality induced by ultraviolet B light (UVB) was prevented with Zn and Se in single or combined pretreatments. Zn ions also protected against the lethality produced by Cu, Al, Cd, Ni, and Pb ions. For the synergic response amphian embryos were subjected to photodynamic treatments plus Zn, UV-B plus Ni and 2,4-D plus Cu resulting in higher lethality than expected from single treatments. The results point out the possibility to evaluate by means of the AMPHITOX test a large number of physico chemical agents with adverse or beneficial effects in relation to oxidative stress as a main mechanisms of toxicity