title: 7,12-Dimethylbenz[a]anthracene inhibition of steroid production in MA-10 mouse Leydig tumor cells is not directly linked to induction of CYP1B1.
abstract: Testosterone, which is essential for spermatogenesis, is synthesized in the Leydig cells of the testis. This study addresses whether male reproductive toxicity from exposure to polycyclic or polychlorinated aromatic hydrocarbons, such as 7,12-dimethylbenz[a]anthracene (DMBA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may be due to direct effects on Leydig cell function. Using a cell-based assay, the effects of TCDD, benz[a]anthracene (BA), and DMBA on steroid production and cytochrome P4501B1 (CYP1B1) expression in treated MA-10 mouse Leydig tumor cells or primary cultures of rat Leydig cells was determined. (Bu)(2)cAMP-stimulated steroid production was inhibited approximately 25% and approximately 80% by DMBA treatment of MA-10 cells and rat Leydig cells, respectively, while BA or TCDD were without effect. Conversely, male Sprague-Dawley rats treated with TCDD displayed a 75% decrease in serum testosterone levels, while DMBA-treated rats had circulating testosterone levels comparable to control rats. Injection of human chorionic gonadotropin (hCG) 1 h prior to euthanasia restored testosterone levels in TCDD-treated rats to 79% of the hCG-stimulated levels in control rats. Steady-state levels of CYP1B1 mRNA, as detected by RT-PCR, are present in the MA-10 cells and treatment with TCDD, BA, DMBA, or the cAMP analog (Bu)(2)cAMP induced CYP1B1 mRNA expression levels. CYP1B1 was constitutively expressed in rat testis, adrenal, liver, and kidney tissues while CYP1A1 was undetectable. TCDD treatment induced CYP1B1 expression in the adrenal and liver and CYP1A1 in the kidney and liver. DMBA treatment induced only CYP1A1 levels in kidney and liver. In sum, DMBA or a reactive DMBA metabolite, but not TCDD, has a direct effect on steroidogenesis in isolated Leydig cells. CYP1B1 expression levels, however, cannot be directly correlated to potential in vitro or in vivo toxic effects of TCDD or DMBA.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Mandal
authors.forename: L R
authors.initials: LR
authors.lastname: McDaniel
authors.forename: R A
authors.initials: RA
authors.lastname: Prough
authors.forename: B J
authors.initials: BJ
authors.lastname: Clark
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000726:Androgen Antagonists / Q000633:toxicity*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001551:Benz(a)Anthracenes / Q000633:toxicity; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D007984:Leydig Cell Tumor / Q000201:enzymology*; D007985:Leydig Cells / Q000187:drug effects / Q000201:enzymology; D008297:Male; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D011374:Progesterone / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
chemical_list: D000726:Androgen Antagonists; D001551:Benz(a)Anthracenes; D006063:Chorionic Gonadotropin; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D013739:Testosterone; D011374:Progesterone; D015127:9,10-Dimethyl-1,2-benzanthracene; D003577:Cytochrome P-450 Enzyme System; C030935:benz(a)anthracene; D000242:Cyclic AMP; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1