Differences between rats and mice in the involvement of the aryl hydrocarbon receptor in 4-vinylcyclohexene diepoxide-induced ovarian follicle loss

Kary E. Thompson, Shannon M. Bourguet, Patricia J. Christian, Jamie C. Benedict, I. Glenn Sipes, Jodi A. Flaws, Patricia B. Hoyer

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Repeated dosing with the occupational chemical 4-vinylcyclohexene diepoxide (VCD) selectively depletes small pre-antral follicles in the ovaries of rats and mice via apoptosis. The aryl hydrocarbon receptor (AhR) plays a role in mediating the effects of several xenobiotics. Therefore, this study was designed to investigate a potential role of the AhR in VCD-induced ovotoxicity. Female F344 rats, C57BL/6 mice, or AhR-deficient (-/-, AhRKO) mice were dosed daily (15 days) with vehicle, VCD (80 mg/kg, i.p.) and/or the AhR antagonist, alpha-naphthoflavone (ANF; 80 mg/kg, i.p.). Compared with controls, VCD caused a 60% reduction (P < 0.05) in primordial and primary follicles in mice and rats. Concurrent dosing with ANF protected against the VCD-induced follicle loss in rats, but not in mice. As with AhR-intact mice and rats, VCD induced a 70% loss (P < 0.05) of small pre-antral follicles in AhRKO mice. AhR mRNA expression was increased (P < 0.05) by VCD dosing in small pre-antral follicles isolated from ovaries of rats but not mice. AhR protein in rats was increased by VCD dosing in oocyte nuclei in primordial and primary follicles when measured by immunofluorescence and confocal microscopy. In rat small pre-antral follicles, apoptosis-associated caspase-3-like activity was increased (P < 0.05) by VCD treatment, decreased (P < 0.05) by ANF treatment, and unaffected by VCD plus ANF treatment. VCD had no effect on expression of GST Ya1 or GST Ya2 mRNA or CYP 1A1 protein in rats. Taken together, these findings demonstrate a difference between rats and mice in the potential involvement of AhR as related to VCD-induced ovotoxicity. Whereas, AhR appears to be involved in rats, no evidence for a similar role in mice was obtained. Overall, these findings point out that there can be mechanistic species differences in ovarian responses to xenobiotic chemicals.

Original languageEnglish (US)
Pages (from-to)114-123
Number of pages10
JournalToxicology and Applied Pharmacology
Volume203
Issue number2
DOIs
StatePublished - Mar 1 2005

Keywords

  • Apoptosis
  • Aryl hydrocarbon receptor
  • Follicle toxicity
  • Pre-antral follicles
  • VCD

ASJC Scopus subject areas

  • Toxicology
  • Pharmacology

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