Seasonal changes in antioxidant defenses of the digestive gland of the brown mussel (Perna perna)

Fifteen specimens of adult mussels Perna perna were analyzed quarterly for antioxidant and detoxifying enzymes (superoxide dismutase, SOD, EC1.15.1.1; catalase, CAT, EC 1.11.1.6, and glutathione S-transferase GST, EC 2.5.1.18 ), and non-enzymatic antioxidants (reduced glutathione, GSH; oxidized gluta thione, GSSG; and total glutathione, TG), thiobarbituric reactive substance s (TBARS) content, and oxygen consumption of the isolated digestive gland. Significant differences (P < 0.05) were found in relation to the variables analyzed during May and December. Except total and reduced glutathione cont ent, the other antioxidants and oxygen consumption were enhanced in May and December compared to March and September (means <plus/minus> S.E.M.; grams of wet weight): Catalase (28.5 +/- 2.7, 22.2 +/- 5.4, and 8.1 +/- 1.7, 9.8 +/- 2.0 mmol min(-1) g(-1), respectively); superoxide dismutase (4208.7 +/ - 400.0, 1543.3 +/- 181.8, and 563.6 +/- 54.5, 863.5 +/- 127.6 USOD g(-1), respectively); glutathione S-transferase (12.0 +/- 2.9, 19.3 +/- 1.2, and 5 .3 +/- 0.46, 4.5 +/- 1.3 mu molmin(-1) g(-1), respectively), and oxygen con sumption (158.3 +/- 4.4, 133.8 +/- 9.4, and 127.9 +/- 7.6, 86.4 +/- 6.9, mu mol O-2 min(-1) g(-1), respectively). TBARS contents showed higher values in May (94.6 +/- 23.7 nmol g(-1)) compared to March (41.0 +/- 3.7 nmol g(-1 )) and September (42.0 +/- 6.8 nmol g(-1)); however, the values found in De cember (52.0 +/- 7.5 nmol g(-1)) were not significantly different from thos e found in September. Higher GSH concentrations were found in December (2.3 1 +/- 0.19 mM), which may account for the decreased TBARS contents found in this period compared to March (GSH 0.90 +/- 0.12 mM) and September (GSH 0. 89 +/- 0.11 mM). Total glutathione content showed a similar pattern to GSH. Oxidized glutathione concentrations showed significant differences only wh en the samples of December (2.2 +/- 0.60 mM) and September (0.66 +/- 0.04 m M) were compared. At December and May, significant increases in practically all the parameters occurred. It is concluded that during December and May, as a result probably of temperature elevation and the intense reproductive activity that follows early summer (December) and autumn (May), the observ ed increase in oxygen consumption is likely to have elicited an increase in cellular oxyradical generation. P. perna seems to seasonally compensate fo r these increases by increasing its antioxidant defenses, (C) 2001 Elsevier Science B.V. All rights reserved.