title: Effects of estrogen coadministration on epoxiconazole toxicity in rats.
abstract: Epoxiconazole (EPX; CAS-No. 133855-98-8) is a triazole class-active substance of plant protection products. At a dose level of 50 mg/kg bw/day, it causes a significantly increased incidence of late fetal mortality when administered to pregnant rats throughout gestation (gestation day [GD] 7-18 or 21), as reported previously (Taxvig et al., 2007, 2008) and confirmed in these studies. Late fetal resorptions occurred in the presence of significant maternal toxicity such as clear reduction of corrected body weight gain, signs of anemia, and, critically, a marked reduction of maternal estradiol plasma levels. Furthermore, estradiol supplementation at dose levels of 0.5 or 1.0 μg/animal/day of estradiol cyclopentylpropionate abolished the EPX-mediated late fetal resorptions. No increased incidences of external malformations were found in rats cotreated with 50 mg/kg bw/day EPX and estradiol cyclopentylpropionate, indicating that the occurrence of malformations was not masked by fetal mortality under the study conditions. Overall, the study data indicate that fetal mortality observed in rat studies with EPX is not the result of direct fetal toxicity but occurs indirectly via depletion of maternal estradiol levels. The clarification of the human relevance of the estrogen-related mechanism behind EPX-mediated late fetal resorptions in rats warrants further studies. In particular, this should involve investigation of the placenta (Rey Moreno et al., 2013), since it is the materno-fetal interface and crucial for fetal maintenance. The human relevance is best addressed in a species which is closer to humans with reference to placentation and hormonal regulation of pregnancy, such as the guinea pig (Schneider et al., 2013).
authors.affiliation: Product Safety, Regulations, Toxicology and Ecology, BASF SE, Ludwigshafen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Stinchcombe
authors.forename: Steffen
authors.initials: S
authors.lastname: Schneider
authors.forename: Ivana
authors.initials: I
authors.lastname: Fegert
authors.forename: Maria Cecilia
authors.initials: MC
authors.lastname: Rey Moreno
authors.forename: Volker
authors.initials: V
authors.lastname: Strauss
authors.forename: Sibylle
authors.initials: S
authors.lastname: Gröters
authors.forename: Eric
authors.initials: E
authors.lastname: Fabian
authors.forename: Karma C
authors.initials: KC
authors.lastname: Fussell
authors.forename: Geoffrey H
authors.initials: GH
authors.lastname: Pigott
authors.forename: Bennard
authors.initials: B
authors.lastname: van Ravenzwaay
mesh_terms: D000818:Animals; D004852:Epoxy Compounds / Q000008:administration & dosage* / Q000633:toxicity*; D004967:Estrogens / Q000008:administration & dosage* / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000002:abnormalities / Q000187:drug effects / Q000473:pathology; D006728:Hormones / Q000097:blood; D006801:Humans; D008297:Male; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D012098:Reproduction / Q000187:drug effects; D014230:Triazoles / Q000008:administration & dosage* / Q000633:toxicity*
chemical_list: D004852:Epoxy Compounds; D004967:Estrogens; D006728:Hormones; D014230:Triazoles; C109476:epoxiconazole