Sparus aurata L. liver EROD and GST activities, plasma cortisol, lactate, glucose and erythrocytic nuclear anomalies following short-term exposure either to 17β-estradiol (E2) or E2 combined with 4-nonylphenol

Immature Sparus aurata L. (gilthead seabream) were exposed to 17β-estradiol (E2) 4000 ng/l and to the same E2 concentration mixed with 50,000 ng/l 4-nonylphenol (E2+NP) during 4, 8, 12 and 16 h. E2 availability and E2 plasma level variations were assessed. Liver biotransformation capacity was measured as ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) activities. Plasma cortisol, lactate and glucose were also determined. Genotoxicity was assessed through erythrocytic nuclear anomalies (ENA) frequency. Liver EROD activity significantly decreased during the whole experiment for both treatments, with the exception of 16 h exposure to E2. Liver GST activity was significantly increased after 8 and 12 h of exposure either to E2 or E2+NP. An endocrine disruption expressed as plasma cortisol decrease was observed after 16 h exposure under both tested conditions, concomitantly with a plasma lactate increase. No genotoxic responses, measured as ENA frequency, were detected. Analyzing the E2 water concentration in aquaria without fish it was demonstrated an intense and fast E2 loss, considerably reducing its availability to fish. In the presence of fish, E2 water levels were drastically reduced after 4 h exposure, being this reduction more pronounced in E2 aquarium when compared to E2+NP aquarium. In addition, it was demonstrated a rapid E2 uptake from the water since the highest E2 plasma concentrations were observed after 4 h exposure, followed by a continuous decrease, which became more pronounced between 8 and 12 h of exposure. Furthermore, during the first 8 h exposure to E2 and E2+NP, seabream plasma E2 concentrations were higher than the initial water exposure concentration. Comparing the E2 plasma levels in both seabream-exposed groups, it was clear that its concentration is always higher in E2+NP-treated fish. Despite the previous results, no significant differences were found in the measured responses between E2 and E2+NP.