Seasonal Variations in the Oxidative Metabolism Related to Fe in the Bivalve Mytilus edulis platensis.

GONZÁLEZ PAULA M.; MALANGA, G.; PUNTARULO S.

La Serena

Congreso; Proceedings to the 5th Physiomar International Meeting: Reproduction, Growth, Bioenergetics and Nutrition, Immune Response and Pathology, Genetics, Genomics and Proteomics, Response to Environmental Changes and Toxicity; 2014

In aquatic organisms, as in other biological systems, Fe through Fenton and Haber-Weiss reactions, can directly generate reactive oxygen species (ROS) due to their direct oxidative potential. Oxidative stress could lead to the overwhelming of the antioxidant systems causing the oxidation of different molecules and cellular dysfunctions. Fe-dependent oxidative metabolism under natural conditions in winter and summer was studied in the digestive gland of the bivalve Mytilus edulis platensis. Adult specimens were brought from the Argentine Sea (San Antonio Oeste, Río Negro). Digestive glands were separated from animals collected in summer (18  3°C) and winter (11  1°C) and frozen in liquid nitrogen until analyses. Total Fe content was measured spectrophotometrically and labile Fe pool (LIP) content was measured spectrofluorometrically. Lipid radical (LR?) content was determined by Electronic Paramagnetic Resonance (EPR). -Tocopherol (-T) content was measured by HPLC. Catalase (CAT) and superoxide dismutase (SOD) activities were assayed spectrophotometrically. Total Fe content was not significantly different between seasons; however, LIP content showed significant differences (30 ± 2 and 41 ± 5 pmol/mg FW in summer and winter, respectively). In samples collected in winter LR? content was increased by 2-fold, meanwhile -T content was increased by 52%, as compared to samples obtained in summer. The oxidative ratio LR?/-T was calculated as an index of oxidative stress in the lipophilic cellular medium, and no significant differences were observed between seasons: (3.7  0.5) x 10-4 and (4.5  0. 2) x 10-4 in summer and winter, respectively. CAT activity was significantly higher in winter (0.42  0.04 pmol/mg prot) than in summer (1.6  0.3 pmol/mg prot); however, SOD activity showed an opposite profile. In aqueous cytosol of tissues from cold water animals, or during winter season where water temperature drops, is to be expected a high O2 solubility; since O2 concentration in seawater is augmented. High tissue concentrations of dissolved O2 may enhance the risk of lipid hydroperoxide formation and exacerbate lipid radical chain propagation, as it was observed in the present study. We suggest that in winter reduced SOD activity, as compared to values in tissues from summer collected animals, may contribute to the O2 accumulation. Moreover, these results suggested the influence of Fe on the oxidative metabolism, which could be involved in the basal stress detected. It is known that O2 facilitates Fe removal from ferritin damaging the protein during the process. This Fe adds to the LIP that would actively catalyze lipid peroxidation, as observed in winter animals. However, the similar value of the oxidative stress index LR?/-T in both seasons suggested that winter specimens may deal adaptively with the generated stress.