Sensitivity of Japanese Quail (Coturnix japonica), Common Pheasant (Phasianus colchicus), and White Leghorn Chicken (Gallus gallus domesticus) Embryos to In Ovo Exposure to TCDD, PeCDF, and TCDF

Abstract

Egg injection studies were performed to confirm a proposed model of relative sensitivity of birds to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this model, species are classified as belonging to one of three categories of sensitivity based on amino acid substitutions in the ligand-binding domain of the aryl hydrocarbon receptor. Embryo lethality and relative potencies of 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) were compared with TCDD for Japanese quail (Coturnix japonica; least sensitive), Common pheasant (Phasianus colchicus; moderately sensitive), and White Leghorn chicken (Gallus gallus domesticus; most sensitive). Doses ranging from 0.044 to 37 pmol/g egg (0.015-12 ng/g egg) were injected into the air cell of eggs prior to incubation. LD(50) (95% confidence intervals) values, based on rate of hatching for TCDD, PeCDF, and TCDF, were 30 (25-36), 4.9 (2.3-9.2), and 15 (11-24) pmol/g egg for the quail, 3.5 (2.3-6.3), 0.61 (0.28-1.2), and 1.2 (0.62-2.2) pmol/g egg for pheasant, and 0.66 (0.47-0.90), 0.75 (0.64-0.87), and 0.33 (0.23-0.45) pmol/g egg for chicken, respectively. LD(50)-based relative potencies of PeCDF and TCDF were 6.1 and 2.0 for quail, 5.7 and 2.9 for pheasant, and 0.88 and 2.0 for chicken, respectively. TCDD was not the most potent compound among the species tested, with PeCDF and TCDF being more potent than TCDD in the quail and pheasant. TCDF was the most potent in chicken. Species sensitivity was as expected for TCDD and TCDF, whereas for PeCDF, the chicken and pheasant were similar in sensitivity and both were more sensitive than the quail. Results from companion in vitro studies are generally similar to those reported here with a few exceptions.

Risk for animal and human health related to the presence of dioxins and dioxin‐like PCBs in feed and food

“…Quail were more resistant than chicken or pheasant to embryotoxicity caused by TCDD, 2,3,4,7,8‐PeCDF, or TCDF after injection of eggs into the air sac in a range of 0.22–37 pmol/g egg with for TCDD‐induced mortality a NOAEL of 1,824 pg/g egg and an LD 50 of 9,700 pg/g. In contrast to chicken, the order of chemical potency was PeCDF > TCDF > TCDD (Cohen‐Barnhouse et al., ). However, with other chronic toxicity endpoints, such as deformities, body and organ weights and histopathology, the comparisons were not as clear as with embryo mortality and could not be used to derive a dose response (Cohen‐Barnhouse et al., ).…”

Tissue‐based risk assessment of great blue heron (Ardea herodias) exposed to PCDD/DF in the Tittabawassee River floodplain, Michigan, USA

“…Recent studies have found that TCDD, TCDF, and 2,3,4,7,8-PeCDF may not be equipotent in birds, as was concluded by the most recent assessment by the WHO [23,[72][73][74]. Based on the results of egg injection studies in Japanese quail [74], a species that falls into the same broad category of sensitivity to dioxin-like compounds as GBH, TCDF and 2,3,4,7,8-PeCDF were found to be twofold and sixfold more potent, respectively, than TCDD at causing embryo lethality. By applying these relative potencies to the concentrations observed in GBH eggs collected in the current study, concentrations expressed as DF-TEQ increased approximately threefold.…”

Uptake of radiolabeled 3,3′,4,4′‐tetrachlorobiphenyl into Japanese quail egg compartments and embryo following air cell and albumen injection

“…Unlike feeding trials, they allow a rapid and cost-effective means of determining toxicity of individual compounds or mixtures. Furthermore, a number of egg injection studies have effectively established the impacts of hydrophilic and hydrophobic vehicles and compounds, including PCBs, dioxins, PBDEs, dibenzofurans, perfluorooctane sulfonate, and methyl mercury [45,51,52,[54][55][56][57][58][69][70][71][72][73][74][75]. These studies have contributed to our understanding of toxicity profiles and measurement endpoints, and have given us data useful in directly estimating the egg concentrations in wild birds and the modes/timing of maternal transfer [10,63].…”