CYP-dependent induction of glutathione S-transferase in Daphnia similis exposed to a disperse azo dye.

Abstract

Disperse Red 1 (DR1) is an azo dye that can reach the aquatic environment through the discharge of textile industrial wastewaters. It has been tested in Daphnia similis and shown to be highly toxic. Cytochrome P450 (CYP) is a class of enzymes involved in phase I of detoxification, while glutathione S-transferase (GST) are a class of phase II enzymes. No information about phase I or II dye metabolism in microcrustacea were found in the literature. In this study we identified CYP and GST enzymes involved in the metabolism of DR1 in juveniles of D. similis. Using spectrophotometric analysis we showed that 50% of the dye was absorbed by the organisms, which could be confirmed by the reddish color of animals exposed to DR1, however adsorption cannot be ruled out. GST activity increased from 280 to 615nmol(-1)min(-1)mg when D. similis were exposed for 48h to 0.2mgL(-1) DR1 and from 274 to 815nmol(-1)min(-1)mg when exposed to 5mgL(-1). Data clearly demonstrate that exposure to DR1 can stimulate a strong induction of GST activity, whose participation in DR1 metabolism needs to be confirmed. The induction of GST activity seems to be dependent on CYP activity, since treatment with SKF535A, a CYP inhibitor, blocked the DR1-dependent GST induction. We speculate that GST is involved in DR1 metabolism in Daphnia and that CYP activity is necessary to induce GST-activity, which is an indirect evidence of its role in the biotransformation of DR1.