Ethoxyresorufin-O-deethylase enzyme activities and accumulation of secondary/tertiary lysosomes in rabbitfish Siganus oramin as biomarkers for xenobiotic exposures Original Research Article

The sensitivities of using hepatic and intestinal ethoxyresorufin-O-deethylase (EROD) activities and hepatic accumulation of secondary/tertiary (2°/3°) lysosomes to detect xenobiotic exposures were assessed in the rabbitfish Siganus oramin in a metropolitan harbour, subtropical Hong Kong, over a complete seasonal cycle of one year. Additional information on the body-burden pollutants and physiological indices in S. oramin, and seasonal variables in seawater quality, were extracted from published data and re-analyzed. Under the influences of pollutant cocktail and seasonal factors, neither the hepatic nor intestinal EROD activity was indicative of total polycyclic aromatic hydrocarbons (∑ PAH), total polychlorinated biphenyls, condition factor and hepatosomatic index (HSI) in S. oramin. However, the relative ratio of hepatic to intestinal EROD activities provided an indication to differentiate the xenobiotic intake route in the fish through diffusion via gills/skin or consumption of contaminated food. In addition, the elevated hepatic accumulation of 2°/3° lysosomes was closely associated with the dominant temporal trends of zinc and ∑ PAH, as well as reduced HSI, in S. oramin. Being minimally influenced by any investigated seasonal factors, the hepatic 2°/3° lysosomes in S. oramin was recommended as an effective biomarker of xenobiotic exposures and toxic effects for use in coastal pollution monitoring programmes.