Toxicity and 7-ethoxyresorufin O-deethylase-inducing potency of coplanar polychlorinated biphenyls (PCBs) in chick embryos

Abstract

The toxicities of the coplanar polychlorinated biphenyls 3,3',4,4'-tetrachlorobiphenyl (TCB), 3,3',4,4',5-pentachlorobiphenyl (PeCB) and 3,3',4,4',5,5'-hexachlorobiphenyl (HCB) were compared in a 72-h study on chick embryos. The substances were injected into the air sacs of hens' eggs preincubated for 7 days. Mortality was measured 72 h later and corresponding LD50 values were calculated. The rank order of toxicity was PeCB greater than TCB greater than HCB. Using the same injection procedure, the potencies of these chlorobiphenyls with regard to their induction of hepatic 7-ethoxyresorufin O-deethylase activity were compared. The ranking order of the substances as inducers was the same as their order when ranked according to toxicity. The three coplanar chlorobiphenyls were considerably more toxic and potent as inducers than the nonplanar 2,2',4,4',5,5'-hexachlorobiphenyl. In a 2-week toxicity study, PeCB and HCB were injected into the yolks of hens' eggs preincubated for 4 days. PeCB was about 50-fold more potent than HCB in causing embryonic death. Both substances caused abnormalities, including edema, liver lesions, microphthalmia and beak deformities.

Inhibition of 3,3′,4,4′,5-Pentachlorobiphenyl-Induced Chicken Embryotoxicity by 2,2′,4,4′,5,5′-Hexachlorobiphenyl

“…This order is similar to the typical Ah receptor-mediated response in the chicken embryo, i.e., cytochrome P4501A1 induction (Brunstrom and Andersson, 1988;Brunstrbm, 1988). The rank order for EROD induction by PCBs is 3, 3',4,4',5-pentaCB > 3,3',4,4'-tetraCB > 3,3',4,4',5,5'-hexaCB (Brunstrom and Andersson, 1988).…”

“…Several studies have reported that the chicken embryo is highly sensitive to the toxic effects of TCDD, coplanar PCB congeners, and related HAHs (Poland and Glover, 1977;Rifkind et al, 1984;Brunstrom and Andersson, 1988). The Ah receptor can be detected in 5-day-old embryos, and although receptor levels are variable in the embryo and neonate (Denison et al, 1986), induction of CYP1A1-dependent activity is observed throughout embryonic development and in the neonate.…”

“…The chick embryo has previously been shown to be highly sensitive to biochemical and toxic responses (such as enzyme induction, embryolethality, malformations, edema, and liver lesions) induced by TCDD and related compounds, and the chicken embryo also expresses the Ah receptor (Denison et ai, 1986;Goldstein et ai, 1976;McKinney et ai, 1976;Poland and Glover, 1977;Schrankel et ai, 1982;Brunstrbm and Danerud, 1983;Rifkind et ai, 1984;Brunstrbm, 1986Brunstrbm, , 1988Brunstrom and Andersson, 1988).…”

Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans and Wildlife

“…Studies with chickens and wild avian species reported in vitro and in ovo effects, with REPs ranging from <0.0003 to 0.15 depending on the species (66,68,69,122,123). A value of 0.05 is recommended.…”

Developmental Toxicity of PCB 126 (3,3′,4,4′,5-Pentachlorobiphenyl) in Nestling American Kestrels (Falco sparverius)

“…Schwartz et al (1993) reported 71 ng/g of PCB congener 126 in a bald eagle egg containing a deformed embryo. This concentration is over 10-fold higher than the LD50 in the chicken egg (Brunstrom and Andersson, 1988) and slightly higher than the LD50 in the American kestrel egg (Hoffman et al, 1995). Best et al (1994) and Bowerman et al (1994) have also related nest productivity to PCB concentrations in bald eagle eggs from the Great Lakes that failed to hatch.…”