The dioxin-like PCB 77 but not the ortho-substituted PCB 153 interferes with chicken embryo thyroid hormone homeostasis and delays hatching.
The effects of the dioxin-like polychlorinated biphenyl (PCB) 77 and the ortho-substituted PCB 153 on thyroid hormone availability were investigated during the last week of embryonic development in chicken. High doses of these PCBs (1microg PCB 77 and 20microg PCB 153) were injected into chicken eggs at day 4 of incubation. Blood and tissue samples were collected from day 14 of incubation until 1 day after hatching. We did not observe influences of PCB 153 on thyroid hormone (TH) levels. Treatment with PCB 77, on the other hand, decreased plasma total T(4) concentrations but increased hepatic T(4) levels at day 14 of incubation. Later in development, at stages near the process of hatching, severe decreases of T(4) and T(3) levels were observed in the PCB 77 group, both in plasma and tissues. PCB 77 severely reduced the TH peak that normally coincides with the stage of internal pipping. This reduction was accompanied by a considerable delay in the moment of hatching. We conclude that the dioxin-like PCB 77, but not the ortho-substituted PCB 153, can decrease TH availability towards the end of embryonic development and hence disturb the process of hatching.
Laboratory of Comparative Endocrinology, K.U.Leuven, Naamsestraat 61, B-3000 Louvain, Belgium. simon.roelens@bio.kuleuven.ac.be
Simon A
SA
Roelens
Veerle
V
Beck
Johan
J
Maervoet
Goele
G
Aerts
Geert E
GE
Reyns
Paul
P
Schepens
Veerle M
VM
Darras
D000818:Animals; D002642:Chick Embryo; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood / Q000187:drug effects* / Q000378:metabolism*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood / Q000187:drug effects* / Q000378:metabolism*
D014284:Triiodothyronine; D011078:Polychlorinated Biphenyls; D013974:Thyroxine; C028451:3,4,3',4'-tetrachlorobiphenyl; C014024:2,4,5,2',4',5'-hexachlorobiphenyl