EMBRYOTOXICITY OF 2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN IN THE RING-NECKED PHEASANT

Abstract

Fertilized eggs of ring-necked pheasants (Phusiunus colchicus) were injected into the albumin or yolk with vehicle or graded doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (0.01, 0.1, 1, 10, 100, 1,000, 10,000, or 100,000 pg TCDD/g egg) on day 0 of embryonic development and toxicity was assessed in 1-d-old hatchlings and 28-d-old chicks. The most sensitive effect of in ovo TCDD exposure was induction of hepatic ethoxyresorufin-0-deethylase (EROD) activity in 1-d-old hatchlings. The ED50 for this response was 312 pg TCDD/g egg. Embryo mortality was the most sensitive sign of toxicity. The TCDD dose that caused 50% mortality above control (LD50) when injected into the egg albumin or yolk was 1,354 and 2,182 pg TCDD/g egg, respectively. At egg TCDD doses up to and including 1,000 pg TCDD/g egg, no effect was detected in 1-d-old hatchlings and 28-d-old chicks in body growth, organ weights, carcass morphometrics, incidence of edema, or incidence of histological alterations in the liver, spleen, heart, Bursa of Fabricius, or thymus. Egg TCDD doses as high as 1,000 pg TCDD/g egg also had no effect on cardiac morphometrics or incidence of cardiac malformations in 1-d-old hatchlings, or on antibody-mediated immunity in 28-d-old chicks. We conclude that embryo mortality is the most sensitive sign of TCDD toxicity in the ring-necked pheasant following in ovo exposure. The ring-necked pheasant embryo is less sensitive than the chicken (Gullus domesticus) embryo and more sensitive than the eastern bluebird (Siuliu siulis) embryo to TCDD toxicity.

Correlation between an in vitro and an in vivo measure of dioxin sensitivity in birds

“…This finding validates the EROD bioassay as a useful method for evaluating the relative sensitivity of dioxin-like compounds in avian species, reducing the need for extensive in vivo toxicity testing. Furthermore, by establishing a correlation between an AHR-mediated biochemical endpoint (EROD) and in vivo toxicity, our results add weight-of-evidence to an emerging EROD EC50 (nM) 10 -2 10 -1 10 0 10 1 LD50 (nmol/kg egg) Kennedy et al (1996a) b Sanderson et al (1998) c Bosveld (1995) d Lorenzen et al (1997) e Head et al (2008) f Nosek et al (1993) g Powell et al (1998) h Brunström (1989) i Hoffman et al (1998) j Normalized to account for different vehicle k Mean of two common tern values is presented in Fig. 2 l Turkey LD50 value was derived by linear interpolation between the LOAEL (20 lg/kg; 36% mortality), and the LD100 (60 lg/kg; 100% mortality) picture of the importance of AHR activation in differential biochemical responses to dioxin-like compounds in birds (Head et al 2008;Karchner et al 2006).…”

“…Some of the LD50 values reported in Fig. 2 were affected by high mortality in the vehicle group or incomplete dose-response curves (Brunström 1989;Nosek et al 1993;Powell et al 1998). EROD data were not always reproducible as demonstrated by the almost 4-fold difference in EC50 values for PCB 126 in two common tern studies (Table 1).…”

BIOLOGICAL EFFECTS OF POLYCHLORINATED DIBENZO-p-DIOXINS, DIBENZOFURANS, AND BIPHENYLS IN BALD EAGLE (HALIAEETUS LEUCOCEPHALUS) CHICKS

“…Except for one edematous chick, no signs were apparent in either the hatched eaglets or in failed eggs of Great Lakes Embryo Mortality, Edema, and Deformities Syndrome (GLE-MEDS) [44], such as reported for fish-eating birds in the Great Lakes and elsewhere [11][12][13][14][15][16][17][18][19][20][21]45], which is similar to the toxic syndrome caused by TCDD in chicken embryos. In embryos of other avian species, such as ring-necked pheasants (Phasianus colchicus), mortality is the most sensitive response to TCDD exposure and the symptoms seen in chickens at lower doses are not observed [46]. However, there were no significant differ- [42].…”

Terrestrial wildlife risk assessment for TCDD in land‐applied pulp and paper mill sludge

“…Egg concentrations are an important endpoint to consider because of the high sensitivity of the developing embryos to TCDD. Nosek [36] performed an egg-injection study on ring-necked pheasants to determine a dose-response relationship for effects of TCDD in the eggs on embryo viability. Nosek [36] determined the NOAEL for embryo viability to be 100 ng/kg.…”

“…Nosek [36] performed an egg-injection study on ring-necked pheasants to determine a dose-response relationship for effects of TCDD in the eggs on embryo viability. Nosek [36] determined the NOAEL for embryo viability to be 100 ng/kg. While egg-injection studies provide measurable exposure levels, they are not the same as the residue from the parent.…”