Weanling female Sprague-Dawley rats are not sensitive to the antiestrogenic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
Investigators have shown that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can inhibit certain estrogenic events in vivo and in vitro. To further investigate this phenomenon, the effects of estradiol (E2) alone or TCDD plus estradiol on several estrogen-dependent parameters were evaluated in weanling female Sprague-Dawley rats. E2 (10 micrograms/kg/day, Postnatal Days (PND) 21 and 22) caused significant increases in relative uterine weight and keratinization of the vaginal epithelium (PND 23). E2 significantly reduced uterine estrogen receptor (ER) protein levels and serum FSH levels, with a trend toward reduction of ER mRNA levels. None of these parameters were affected by pretreatment with 20, 40, or 80 micrograms/kg TCDD (PND 19). Uterine progesterone receptor levels were not affected by E2 or TCDD in the present study. In contrast, TCDD significantly decreased body weight (40 or 80 micrograms/kg) by PND 21, significantly decreased relative thymic weights, and significantly increased relative hepatic weights (20, 40, and 80 micrograms/kg, by PND 23). In addition, TCDD dramatically induced CYPIA1 hepatic mRNA levels, indicating that TCDD was properly delivered and could mediate other well-documented Ah receptor-dependent events. Thus, weanling female Sprague-Dawley rats are not sensitive to the antiestrogenic effects of TCDD at doses which cause overt toxicity. The results provide evidence that the previously reported antiestrogenic effects of TCDD are probably species, strain, and age dependent.
White
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Department of Environmental Medicine, University of Rochester Medical Center, New York 14642, USA.
Rucci
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Liu
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Gasiewicz
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D000818:Animals; D001665:Binding Sites; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004347:Drug Interactions; D004848:Epithelium / Q000187:drug effects / Q000473:pathology; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D008099:Liver / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000187:drug effects* / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism; D014621:Vagina / Q000187:drug effects* / Q000473:pathology; D014886:Weaning
D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D004958:Estradiol; D005640:Follicle Stimulating Hormone; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1