title: Acute 7,12-dimethylbenz[a]anthracene exposure causes differential concentration-dependent follicle depletion and gene expression in neonatal rat ovaries.
abstract: Chronic exposure to the polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene (DMBA), generated during combustion of organic matter including cigarette smoke, depletes all ovarian follicle types in the mouse and rat, and in vitro models mimic this effect. To investigate the mechanisms involved in follicular depletion during acute DMBA exposure, two concentrations of DMBA at which follicle depletion has (75 nM) and has not (12.5 nM) been observed were investigated. Postnatal day four F344 rat ovaries were maintained in culture for four days before a single exposure to vehicle control (1% DMSO; CT) or DMBA (12 nM; low-concentration or 75 nM; high-concentration). After four or eight additional days of culture, DMBA-induced follicle depletion was evaluated via follicle enumeration. Relative to control, DMBA did not affect follicle numbers after 4 days of exposure, but induced large primary follicle loss at both concentrations after 8 days; while, the low-concentration DMBA also caused secondary follicle depletion. Neither concentration affected primordial or small primary follicle number. RNA was isolated and quantitative RT-PCR performed prior to follicle loss to measure mRNA levels of genes involved in xenobiotic metabolism (Cyp2e1, Gstmu, Gstpi, Ephx1), autophagy (Atg7, Becn1), oxidative stress response (Sod1, Sod2) and the phosphatidylinositol 3-kinase (PI3K) pathway (Kitlg, cKit, Akt1) 1, 2 and 4 days after exposure. With the exception of Atg7 and cKit, DMBA increased (P < 0.05) expression of all genes investigated. Also, BECN1 and pAKT(Thr308) protein levels were increased while cKIT was decreased by DMBA exposure. Taken together, these results suggest an increase in DMBA bioactivation, add to the mechanistic understanding of DMBA-induced ovotoxicity and raise concern regarding female low concentration DMBA exposures.
authors.affiliation: Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
authors.forename: Jill A
authors.initials: JA
authors.lastname: Madden
authors.affiliation: Department of Physiology, University of Arizona, Tucson, AZ 85724, USA.
authors.forename: Patricia B
authors.initials: PB
authors.lastname: Hoyer
authors.affiliation: INRS-Institut Armand-Frappier Research Centre, University of Quebec, Laval, QC H7V 1B7, Canada.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Devine
authors.affiliation: Department of Animal Science, Iowa State University, Ames, IA 50011, USA; Department of Physiology, University of Arizona, Tucson, AZ 85724, USA. Electronic address: akeating@iastate.edu.
authors.forename: Aileen F
authors.initials: AF
authors.lastname: Keating
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D000831:Animals, Newborn; D001343:Autophagy / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004851:Epoxide Hydrolases / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D005982:Glutathione Transferase / Q000235:genetics; D006080:Ovarian Follicle / Q000187:drug effects; D010053:Ovary / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D015127:9,10-Dimethyl-1,2-benzanthracene; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D004851:Epoxide Hydrolases
keywords: DMBA; Follicle; Ovary