title: Genomic biomarkers of phthalate-induced male reproductive developmental toxicity: a targeted RT-PCR array approach for defining relative potency.
abstract: Male rat fetuses exposed to certain phthalate esters (PEs) during sexual differentiation display reproductive tract malformations due to reductions in testosterone (T) production and the expression of steroidogenesis- and INSL3-related genes. In the current study, we used a 96-well real-time PCR array containing key target genes representing sexual determination and differentiation, steroidogenesis, gubernaculum development, and androgen signaling pathways to rank the relative potency of several PEs. We executed dose-response studies with diisobutyl (DIBP), dipentyl (DPeP), dihexyl (DHP), diheptyl (DHeP), diisononyl (DINP), or diisodecyl phthalate (DIDP) and serial dilutions of a mixture of nine phthalates. All phthalates, with the exception of DIDP, reduced fetal testicular T production. Several genes involved in cholesterol transport, androgen synthesis, and Insl3 also were downregulated in a dose-responsive manner by DIBP, DPeP, DHP, DHeP, DINP, and the 9-PE mixture. Despite speculation of peroxisome proliferator activated receptor (PPAR) involvement in the effects of PEs on the fetal testis, no PPAR-related genes were affected in the fetal testes by exposure to any of the tested PEs. Furthermore, the potent PPARα agonist, Wy-14,643, did not reduce fetal testicular T production following gestational day 14-18 exposure, suggesting that the antiandrogenic activity of PEs is not PPARα mediated. The overall sensitivity of the fetal endpoints (gene expression or T production) for the six phthalates from most to least was Cyp11b1 > Star = Scarb1 > Cyp17a1 = T production > Cyp11a1 = Hsd3b = Insl3 > Cyp11b2. The overall potency of the individual phthalates was DPeP > DHP > DIBP ≥ DHeP > DINP. Finally, the observed mixture interaction was adequately modeled by the dose-addition model for most of the affected genes. Together, these data advance our understanding of the collective reproductive toxicity of the PE compounds.
authors: Reproductive Toxicology Branch, Toxicology Assessment Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
authors: Bethany R
authors: BR
authors: Hannas
authors: Christy S
authors: CS
authors: Lambright
authors: Johnathan
authors: J
authors: Furr
authors: Nicola
authors: N
authors: Evans
authors: Paul M D
authors: PM
authors: Foster
authors: Earl L
authors: EL
authors: Gray
authors: Vickie S
authors: VS
authors: Wilson
mesh_terms: D000818:Animals; D015509:Developmental Biology / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005819:Genetic Markers; D005865:Gestational Age; D008297:Male; D018811:Maternal Exposure; D008962:Models, Theoretical; D010795:Phthalic Acids / Q000633:toxicity*; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012098:Reproduction / Q000187:drug effects* / Q000235:genetics; D018570:Risk Assessment; D013737:Testis / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D013739:Testosterone / Q000378:metabolism; D046509:Tissue Culture Techniques; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D005819:Genetic Markers; D010795:Phthalic Acids; D013739:Testosterone