CONICET | Buscador de Institutos y Recursos Humanos

The freshwater gastropod Pomacea canaliculata fulfills the ideal conditions of abioindicator species since its digestive gland bioconcentrates elements toxic forhuman and ecosystems health. The aim of this work was to study the balancebetween production of free radicals and antioxidant defenses, and the generationof oxidative damage in the digestive gland of this mollusk after exposure (96 h) tothree elements with differential affinities for functional biological groups: mercury(5.5 μg/L of Hg+2 as HgCl2), arsenic [500 μg/L of (AsO4)−3 as Na3AsO47H2O], oruranium [700 μg/L of (UO2)+2 as UO2(CH2COOH)2]. Bioconcentration factors ofHg, As, and U were 25, 23, and 53, respectively. Snails exhibited a sustainedincrease of reactive species (RS), and protein and lipid damage. Lipid radicalsincreased between 72 and 96 h, respectively, in snails exposed to U and Hg whilethis parameter changed early (24 h) in As- exposed snails. Snails showed proteindamage, reaching maximum values at different endpoints. This redox disbalancewas partially compensated by non-enzymatic antioxidant defenses α-tocopherol(α-T), β-carotene (β-C), uric acid, metallothionein (MTs). Snails consumed α-T andβ-C in an element-dependent manner. The digestive gland consumed rapidly uricacid and this molecule was not recovered at 96 h. Digestive gland showed asignificant increase in MTs after elemental exposure at different endpoints. Theenzymatic antioxidant defenses, represented by the catalase and glutathione-Stransferaseactivities, seems to be not necessary for the early stages of theoxidative process by metals. This work is the first attempt to elucidate cellularmechanisms involved in the tolerance of this gastropod to non-essentialelements. The bioconcentration factors and changes in the oxidative statusand damage confirm that this species can be used as a bioindicator species ofmetal pollution in freshwater bodies.

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