Temporal changes of ethoxyresorufin-O-deethylase (EROD) activities and lysosome accumulation in intestine of fish on chronic exposure to dietary benzo[a]pyrene: Linking erod induction to cytological effects

Temporal changes of intestinal and hepatic ethoxyresorufin-O-deethylase (EROD) activities and quantitative changes of secondary and tertiary (e.g., 2°/3°) lysosomes in enterocytes were compared for the juvenile grouper (Epinephelus coioides) on chronic exposure to foodborne benzo[a]pyrene (BaP) at two environmentally realistic levels (0.25 and 12.5 μg/g fish/d) over a four-week exposure and four-week depuration period. Intestinal EROD induction was rapid (within 3 d) and sustained in the BaP-exposed fish, while a fast recovery (within one week) was observed on withdrawal of BaP intake. A dose-response relationship was demonstrated between intestinal EROD activities and the levels of foodborne BaP. Conversely, hepatic EROD induction was weak and subsided rapidly in the exposed fish, signifying that hepatic EROD activity is not a good indicator of oral intake of BaP. Significant increase of 2°/3° lysosomes, as measured by Vν_{(lysosome, mucosa)}, was detected in young enterocytes of fish in the high-dosing group (12.5 μg/g fish/d) at exposure day 3 and persisted until recovery week 2. Importantly, intestinal EROD activity was significantly correlated to 2°/3° lysosome accumulation in enterocytes (r = 0.571, p <0.001). These results further corroborate our earlier findings that induction of EROD activities in fish do not merely indicate exposure to BaP but also are correlated to harmful biological effects. We recommend the use of these two biochemical and cytological changes in intestines as specific biomarkers to indicate current and recent exposure of fish to BaP via oral intake. © 2006 SETAC.