TY - JOUR
T1 - Effects of gestational and lactational exposure to coplanar polychlorinated biphenyl (PCB) congeners or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thyroid hormone concentrations in weanling rats
AU - Seo, Byung Woun
AU - Li, Mei Hui
AU - Hansen, Larry G.
AU - Moore, Robert W.
AU - Peterson, Richard E.
AU - Schantz, Susan L.
N1 - Funding Information:
The authors thank Carol Davis and Patricia Weston for their assistancein conducting the RIAs. We area lsog ratefult o NIDDK and theN a-tionalH ormonea nd PituitaryP rogramf or theg ift of the TSH RIA kit. This work was supportedb y Health Canada Project #4028t o SLS and NIH Grant #ES01332to REP.
PY - 1995/8
Y1 - 1995/8
N2 - Perinatal exposure to polychlorinated biphenyl (PCB) mixtures or to certain ortho-substituted PCB congeners dramatically reduces circulating thyroxine (T4) concentrations. It is not clear whether perinatal exposure to coplanar PCBs or2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has a similar effect. In this study, time-mated Sprague-Dawley rats were dosed with 2 or 8 mg/kg/day PCB 77 (3,3′,4,4′-tetrachlorobiphenyl), 0.25 or 1.00 μ/kg/day PCB 126 (3,3′,4,4′,5-pentachlorobiphenyl), 0.025 or 0.10 μg/kg/day TCDD, or corn oil vehicle orally on gestation days 10-16. At weaning, plasma total T4 concentrations in PCB 77 and TCDD high-dose female pups were significantly depressed, but the changes were modest (84.4 and 79.6% of control, respectively). T4 concentrations in PCB 126 high-dose females and all high-dose males were also depressed slightly, but the changes were not statistically significant. UDP-Glucuronosyl transferase (UDP-GT) activity towards 4-nitrophenol was increased in all high-dose groups. Thus, the modest decreases in T4 could be due in part to increased T4 glucuronidation by UDP-GT. Triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations were unchanged in all groups. In contrast to the minor changes in thyroid hormone status, liver microsomal ethoxyresorufin-O-deethylase (EROD) was markedly induced in all exposure groups and thymus weights were depressed in the high-dose groups. Because doses of coplanar PCBs or TCDD that caused marked induction of EROD activity had only minor effects on T4, we conclude that changes in thyroid hormone status at weaning are not among the more sensitive effects of perinatal exposure to these compounds.
AB - Perinatal exposure to polychlorinated biphenyl (PCB) mixtures or to certain ortho-substituted PCB congeners dramatically reduces circulating thyroxine (T4) concentrations. It is not clear whether perinatal exposure to coplanar PCBs or2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has a similar effect. In this study, time-mated Sprague-Dawley rats were dosed with 2 or 8 mg/kg/day PCB 77 (3,3′,4,4′-tetrachlorobiphenyl), 0.25 or 1.00 μ/kg/day PCB 126 (3,3′,4,4′,5-pentachlorobiphenyl), 0.025 or 0.10 μg/kg/day TCDD, or corn oil vehicle orally on gestation days 10-16. At weaning, plasma total T4 concentrations in PCB 77 and TCDD high-dose female pups were significantly depressed, but the changes were modest (84.4 and 79.6% of control, respectively). T4 concentrations in PCB 126 high-dose females and all high-dose males were also depressed slightly, but the changes were not statistically significant. UDP-Glucuronosyl transferase (UDP-GT) activity towards 4-nitrophenol was increased in all high-dose groups. Thus, the modest decreases in T4 could be due in part to increased T4 glucuronidation by UDP-GT. Triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations were unchanged in all groups. In contrast to the minor changes in thyroid hormone status, liver microsomal ethoxyresorufin-O-deethylase (EROD) was markedly induced in all exposure groups and thymus weights were depressed in the high-dose groups. Because doses of coplanar PCBs or TCDD that caused marked induction of EROD activity had only minor effects on T4, we conclude that changes in thyroid hormone status at weaning are not among the more sensitive effects of perinatal exposure to these compounds.
KW - PCBs
KW - Perinatal
KW - Rat
KW - TCDD
KW - Thyroid
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U2 - 10.1016/0378-4274(95)03329-J
DO - 10.1016/0378-4274(95)03329-J
M3 - Article
C2 - 7624895
AN - SCOPUS:0029059424
SN - 0378-4274
VL - 78
SP - 253
EP - 262
JO - Toxicology Letters
JF - Toxicology Letters
IS - 3
ER -