Mandal P K, McDaniel L R, Prough R A, Clark B J
Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Toxicol Appl Pharmacol. 2001 Sep 15;175(3):200-8. doi: 10.1006/taap.2001.9241.
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.
对于精子发生至关重要的睾酮是在睾丸的间质细胞中合成的。本研究探讨了接触多环或多氯代芳烃（如7,12 - 二甲基苯并[a]蒽（DMBA）或2,3,7,8 - 四氯二苯并 - p - 二恶英（TCDD））所导致的雄性生殖毒性是否可能归因于对间质细胞功能的直接影响。使用基于细胞的分析方法，测定了TCDD、苯并[a]蒽（BA）和DMBA对经处理的MA - 10小鼠间质细胞瘤细胞或大鼠间质细胞原代培养物中类固醇生成和细胞色素P4501B1（CYP1B1）表达的影响。用DMBA处理MA - 10细胞和大鼠间质细胞后，（Bu）₂cAMP刺激的类固醇生成分别被抑制了约25%和约80%，而BA或TCDD则无此作用。相反，用TCDD处理的雄性Sprague - Dawley大鼠血清睾酮水平下降了75%，而用DMBA处理的大鼠循环睾酮水平与对照大鼠相当。在安乐死前提注人绒毛膜促性腺激素（hCG）1小时可使TCDD处理的大鼠的睾酮水平恢复至对照大鼠hCG刺激水平的79%。通过逆转录 - 聚合酶链反应（RT - PCR）检测到，MA - 10细胞中存在CYP1B1 mRNA的稳态水平，用TCDD、BA、DMBA或cAMP类似物（Bu）₂cAMP处理可诱导CYP1B1 mRNA表达水平。CYP1B1在大鼠睾丸、肾上腺、肝脏和肾脏组织中组成性表达，而未检测到CYP1A1。TCDD处理可诱导肾上腺和肝脏中CYP1B1的表达以及肾脏和肝脏中CYP1A1的表达。DMBA处理仅诱导肾脏和肝脏中CYP1A1的水平。总之，DMBA或一种活性DMBA代谢物而非TCDD对分离的间质细胞中的类固醇生成有直接影响。然而，CYP1B1表达水平与TCDD或DMBA的潜在体外或体内毒性作用并无直接关联。
Zotero 插件