Antioxidant responses and oxidative stress after microcystin exposure in the hepatopancreas of an estuarine crab species.

Antioxidant responses and oxidative stress were evaluated in the hepatopancreas of the estuarine crab Chasmagnathus granulatus (Decapoda, Brachyura) after oral microcystin administration. Responses were evaluated through antioxidant enzyme activities (catalase-(CAT), superoxide dismutase, glutathione-S-transferase- (GST)). Nonproteic sulfhydril (NP-SH) groups, oxygen consumption, lipid peroxides (LPO), and oxidized proteins were also measured. Microcystin administration increased the oxygen consumption. GST activity and NP-SH concentration showed transient increases and CAT activity showed a peak and then a reduction. Oxidative damage was evidenced with regard to LPO content and suggested by the inhibition of CAT activity at the end of the experiment, indicating that the antioxidant response induced by the toxin was insufficient. A lowering in the number of hepatopancreatic B cells should be related to microcystin elimination.

Antioxidant responses after microcystin exposure in gills of an estuarine crab species pre-treated with vitamin E.

Microcystins are hepatotoxins suspected to generate oxidative stress. This mechanism was evaluated in gills of the estuarine crab Chasmagnathus granulatus (Decapoda, Brachyura). Adult male crabs were fed ground beef with or without vitamin E (600 mg/kg). Microcystin (1.21 microg/kg) was daily administered through forced ingestion, for 7 days. After exposure, catalase activity was reduced in posterior gills of crabs supplemented with vitamin E. A lower increment in glutathione S-transferase activity (GST) was observed in organisms pretreated with vitamin E and then exposed to microcystin with respect to those exposed to the toxin but not pretreated with the vitamin. Pretreatment with vitamin E also increased nonproteic sulfhyrdil groups and this effect was not observed after microcystin exposure. The fact that supplementation with antioxidants such as vitamin E modulates GST activity indicates the direct or indirect involvement of microcystin in oxidative stress generation.