Physiological and antioxidant enzyme responses to acute and chronic exposure of Laeonereis acuta (Polychaeta, Nereididae) to copper

Abstract

Chronic (14 days) and acute (48 h) copper effects on the antioxidant defense system and some physiological variables of Laeonereis acuta (Polychaeta, Nereididae) were evaluated. In both assays, two nominal copper concentrations (chronic: C1 = 31.25 and C2 = 62.50 Ag/l; acute: A1 = 250 and A2 = 500 Ag/l) and one control group (Cc and Ac=0 Ag/l) were tested. End points analyzed were antioxidant enzyme activity (catalase, CAT; superoxide dismutase, SOD; and glutathione Stransferase, GST), oxygen consumption, metahemoglobin concentration, and lipid peroxidation (LPO). In the chronic assay, CAT activity was significantly higher in worms exposed to both concentrations of copper tested (C1 = 3.36F0.07 U CAT/mg protein; C2 = 4.06 0.32 U CAT/mg protein) than in control worms (Cc = 2.16F0.39 U CAT/mg protein). SOD activity was also increased in the two copper-exposed groups (C1 = 16.85F4.22 U SOD/mg protein; C2 = 38.19F4.31 U SOD/ mg protein) than in control group (Cc = 3.54F0.46 U SOD/mg protein). However, GST activity was increased only in worms exposed to the higher copper concentration (C2 = 0.022F9.10 _ 4 U GST/mg protein) when compared to the other groups tested (Cc = 0.012F3.10 _ 3 U GST/mg protein; C1 = 0.016F9.10 _ 4 U GST/mg protein). None of the physiological variables analyzed (oxygen consumption, metahemoglobin concentration, and lipid peroxidation) was affected by chronic copper exposure. In the acute assay, only GST activity was induced in worms exposed to copper. This induction was observed only in the A1 group (0.027F2.10 _ 3 U GST/mg protein) when compared to Ac (0.017F2.10 _ 3 U GST/mg protein) or A2 (0.016F7.10 _ 4 U GST/mg protein) groups. On the other hand, lipid peroxidation was higher in A2 (481.9F49.2 nmol CHP/g ww) than in control worms (Ac = 337.9F25.0 nmol CHP/g ww). Oxygen consumption was higher in worms acutely exposed to the lower copper concentration tested (A1 = 0.27F0.04 mg O2/g ww/h) than in the higher concentration (A2 = 0.14F0.01 mg O2/g ww/h). Changes in the swimming behavior of copperexposed animals in both assays and edemas in the body wall of worms acutely exposed to copper were also observed. Results suggest that copper exposure favors reactive oxygen species generation and that enzymatic defense system is induced under chronic exposure, preventing oxygen consumption changes and lipid peroxidation and metahemoglobin formation. However, in acutely exposed worms, in spite of a transient peak of GST activity, no induction of antioxidant enzymes occurs, leading to morphological and physiological changes.