Sensitivity of Common Tern (Sterna hirundo) Embryo Hepatocyte Cultures to CYP1A Induction and Porphyrin Accumulation by Halogenated Aromatic Hydrocarbons and Common Tern Egg Extracts

Abstract.

Experiments were conducted to compare the sensitivity of primary cultures of common tern (Sterna hirundo) and chicken (Gallus domesticus) embryo hepatocytes to cytochrome P4501A (CYP1A) induction and porphyrin accumulation after exposure to halogenated aromatic hydrocarbons (HAHs) or tern egg extracts. The HAHs tested were 2,3,7,8-tetrachlorodibenzo-p -dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF) 3,3′,4,4′-tetrachlorobiphenyl (PCB 77; IUPAC nomenclature), 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126), 3,3′,4,4′,5,5′-hexachlorobiphenyl (PCB 169) and Aroclor® 1254 (a commercial mixture of PCBs). Extracts were prepared from common tern eggs collected from three sites in the Great Lakes basin and one reference site on the east coast of Canada. CYP1A induction was assayed as ethoxyresorufin-O-deethylase (EROD) activity and/or immunodetectable CYP1A protein, and total intracellular porphyrin accumulation was measured fluorometrically. Unlike chicken embryo hepatocyte (CEH) cultures, no intracellular porphyrin accumulation was observed after treatment of tern embryo hepatocyte (TEH) cultures with HAHs or egg extracts. TEH cultures were ∼50 to >1600 times less sensitive than CEH cultures to HAH-mediated CYP1A induction. In contrast, TEH cultures were either approximately equally sensitive or only 3.5–15 times less sensitive than CEH cultures to CYP1A induction mediated by tern egg extracts. These data suggest that common tern embryos may be more susceptible to the CYP1A inducing effects mediated by complex mixtures of environmental contaminants than indicated by their response to individual HAHs.