Disposition and cellular binding of ³H-benzo(a)pyrene at subzero temperatures: studies in an aglomerular arctic teleost fish – the polar cod (Boreogadus saida)

Abstract

Autoradiography at different levels of resolution was used to study the disposition of the polycyclic aromatic hydrocarbon benzo(a)pyrene (³H-BaP) in juvenile and sexually mature polar cod (Boreogadus saida). Exposure took place via the water or after intragastric administration at subzero temperatures. In water-exposed fish, high total tissue levels were found in the gills, olfactory organ, anterior kidney, liver, skin and intestinal wall. Only traces of radioactivity were present in the muscle, brain and gonads. No major differences in tissue levels or in general distribution pattern between males, females or juvenile fish were observed. The gills appeared to be the absorption site for exposure via water. After oral administration, tissue levels of ³H-BaP-derived radioactivity were negligible. Following both administration routes, levels of radioactivity were highest in the bile and intestinal contents while only traces were observed in the urine, indicating biliary excretion as the major excretory pathway in this aglomerular species. Tape-section autoradiography of fish exposed via water revealed tissue-bound residues of ³H-BaP in the olfactory organs, gills, kidney, liver, skin and intestinal mucosa. Light-microscopy autoradiography demonstrated that the bound residues in the olfactory organ, gills and anterior kidney were localized in epithelial cells, while those in liver and intestinal mucosa were evenly distributed. In conclusion, the present study shows that BaP is absorbed from the water via the gills at subzero temperatures, that tissue levels are considerably higher after water exposure than after dietary exposure, that biliary excretion is predominant and, finally, that site-specific tissue binding in the olfactory organs, gills and anterior kidney is confined to epithelial cells.