PARENT SESSION
1D Bioassays for specific hazards (estrogenic effects, genotoxicity, neurotoxicity, ...)
9:00 AM to 7:00 PM, Tuesday, 08 May 2001

(T/EH086) The beneficial effect of Zinc on the lipoperoxidation exerted by Copper in Bufo arenarum embryos.

Fridman, O.¹, Pérez-Coll, C.¹, D'Eramo, J.¹, Herkovits, J.¹, ¹

ABSTRACT- Lipoperoxidation could result from oxidative stress processes exerted by different chemicals including transitional metals. In previous works it was reported a beneficial effect of zinc against the toxicity exerted by copper in Bufo arenarum embryos. In this study the effect of copper and zinc on lipoperoxidation was evaluated administrating these metals in single or combined treatments. Batches of 50 embryos in 200mL of Holtfreter Solution (HS) were treated in the following conditions expressed in mg/L: ( A) 0.2 Cu2+ , (B) 1 Zn2+, (C) 10 Zn2+, (D) 0.2 Cu2+ plus 1 Zn2+, (E) 0.2 Cu2+ plus 10 Zn2+, (F) Control in HS. Embryo survival was recorded at 6 and 144 hours of exposure resulting in 100% in all conditions and at that exposure times, for lipoperoxidation measurements, 10 embryos from each group were homogenised in EDTA-glutathion buffer and based on the reaction between malondialdehyde (MDA) and thiobarbituric acid the thiobarbituric acid-reactive substances (TBARS) were determined with a spectrofluorimeter at wavelengths of 525 nm for excitation and 547 nm for emission.. The lipoperoxidation measured as TBARS (fmol/embryo) in per cent respect to the controls were at 6 and 144 hours of exposure: A 171,6 and 88,2; B 84,7 and 61,8; C 157,3 and 80,9; D 108,1 and 108,8; E 87,1 and 105,9 respectively. Copper, as expected, exerted an oxidative stress within 6 hours of exposure but the organism recovered to normal peroxidation levels after 6 days of treatment which seems to reflect an adaptative response to this metal. Zinc in low concentrations exerted an antioxidant effect both at 6 and 144hours of exposure. Higher concentration of zinc seems to exert an early oxidative effect which diminish to lower peroxidation values than controls after 6 days of treatment. Zinc in high concentrations, in spite of enhancing lipoperoxidation, exert a beneficial effect against copper toxicity. At 144 hours of treatment in all conditions the lipoperoxidation values did not differ significantly from controls which could mean that Bufo arenarum embryos became adapted to the copper as well as zinc in subletal concentrations.

Key words: lipoperoxidation, amphibian, copper, zinc