Effect of sodium chloride on oxidative stress biomarkers of the freshwater bivalve Anodonta cygnea

Abstract

For the first time a study was conducted of the effects of the change in the concentration of sodium chloride in water on the biomarkers of oxidative stress (enzymes: catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST), and the levels of reduced glutathione (GSH), and a marker of peroxidation lipids (LPO) – malonic dialdehyde (MDA)) in the gills of the freshwater mollusc Anodonta cygnea. Adult specimens of A. cygnea of both sexes with a shell length of 70–100 mm were selected for the study, a total of 36 individuals. The molluscs were collected in one of the bays on the southwestern coast of the Volga reaches of the Rybinsk Reservoir (reservoir of the cascade of the upper Volga). The molluscs were kept in the laboratory in aquariums with river water and sand collected from the place of the molluscs' collection. During the experiment, a solution of NaCl 3 g/l in river water was introduced into the container with molluscs. Samples of molluscs’ tissues were taken before application of the saline solution, 40 and 120 min after changing the salt concentration to 3 g/l, and 20 and 60 min after changing the NaCl solution to river water. The change in the concentration of NaCl in water (0–3 g/l) did not affect the content of water-soluble protein in the gills of molluscs during short-term exposure. The change in NaCl concentration in water caused the intensification of LPO processes in the gills of A. cygnea. The change in the activity of the enzymes of the antioxidant system and the increase in the concentration of GSH in A. cygnea gills, indicates their involvement in protecting freshwater molluscs from NaCl-induced oxidative stress. The change in the functioning of the glutathione system may be a compensatory mechanism for changing the NaCl concentration in water. Such biomarkers of oxidative stress as malonic dialdehyde and enzymes of the antioxidant system are sensitive indicators of changes in NaCl concentration in water in freshwater bivalve molluscs, for example A. cygnea.