CYP1B1 expression in rat testis and Leydig cells is not inducible by aryl hydrocarbon receptor agonists

Abstract

1. Cytochrome P450 1B1 (CYP1B1) is highly expressed in testis, but there is conflicting information regarding the inducibility of testicular CYP1B1 by aryl hydrocarbon receptor (AhR) agonists.

2. To assess AhR-mediated regulation, testicular CYP1B1 expression was measured following treatment of adult rats with 3-methylcholanthrene and various dosages of benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The effect of TCDD on CYP1B1 expression in R2C rat Leydig and MA-10 mouse Leydig cells in culture was also determined.

3. Immunoblot analysis showed that treatment with benzo[a]pyrene at dosages up to 200 mg/kg/day and 3-methylcholanthrene at 25 mg/kg/day did not induce testicular CYP1B1 expression. Treatment with TCDD at dosages of 1, 5 or 100 μg/kg had no effect, but testicular CYP1B1 protein levels were increased by approximately 50% at dosages of 10 and 50 μg/kg.

4. CYP1B1 mRNA levels in MA-10 and CYP1B1 protein levels in R2C cells were not induced by exposure to TCDD (10–1000 nM).

5. Overall, the results indicate that rodent testicular CYP1B1 is not inducible by AhR agonists.

Keywords::

• Cytochrome P450 (CYP)
• aryl hydrocarbon receptor (AhR)
• 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
• reverse transcription-polymerase chain reaction (RT-PCR)

Acknowledgements

The authors thank Dr. Mario Ascoli (University of Iowa, IA) for providing MA-10 mouse Leydig tumour cells. The authors also thank Dr. Eugene Hrycay, Ms. Grace Leung and Mr. Leo Yoshida (University of British Columbia) and Ms. Sarah Maines-Bandiera (British Columbia Cancer Agency) for their help with some of the experiments. S.D. received a training grant from Merck Research Laboratories (Merck & Co., Inc., NJ). T.K.H.C. received a Senior Scholar Award from the Michael Smith foundation for Health Research. This work was supported in part by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada (Grant RGPIN 138733-01) and the Canadian Institutes of Health Research (Grant MOP-84581). Preliminary results of this study were presented at the 15th North American ISSX Meeting, Oct. 12-16, 2008, San Diego, CA, and published as an abstract (Deb S and Bandiera SM, Drug Metab Rev 40(Suppl 3):71, 2008).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.