Toxicological assessment of hexachlorobiphenyl isomers and 2,3,7,8-tetrachlorodibenzofuran in chicks

CYP1A in TCDD Toxicity and in Physiology–with Particular Reference to CYP Dependent Arachidonic Acid Metabolism and other Endogenous Substrates

“…Examples of correlations for CYP1A induction and toxicity are: CYP1A in vascular endothelium with mortality in zebrafish and lake trout (Guiney et al, 1997(Guiney et al, , 2000, in liver of young chick embryos with early developmental TCDD toxicity (Walker et al, 1997), in liver of chick embryos close to hatching with hepatic histologic changes and cardiac contractile dysfunction (Rifkind et al, 1984;Canga et al, 1988Canga et al, , 1993, in liver of post-hatched chicks and rats with porphyria (Goldstein et al, 1976;Jacobs et al, 1990), in mouse liver, with suppression of phosphoenolpyruvate kinase (PEPCK) activity (Weber et al, 1995). ED 50 values were the same for TCDD induction of the Cyp1A1, Cyp1A2, and PEPCK1 genes in mouse liver (Boverhof et al, 2005).…”

Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife.

“…Although many studies with young or adult birds have shown dioxinlike toxic and biochemical effects of TCDD and PCBs, these studies were not designed for REPs of compounds to be reliably derived (56)(57)(58)(59)(60)(61)(62)(63). At present, TEFs for birds can only be derived from egg injection studies, studies with cultured avian hepatocytes, and studies with cultured thymus cells.…”

Chemistry of PCBs and PBBs

“…Recent work with five symmetrical hexachlorobiphenyl isomers in chicks (25,26) and in mice (27) has demonstrated that separate and distinct differences in isomer toxicity are possible and that the differences are related to chemical structure via effects of varying chlorine substitution on compound lipophilicity and metabolism. The hexachloro isomers studied were 3,4,5,3',4',5'-; 2,4,6,2',4',6'-; 2,3,-4,2',3',4'-; 2,4,5,2',4',5'-; 2,3,6,2'3',6'-and 2,3,-5,2',3',5'-chloro compounds.…”