Characterization of a new cytochrome P450 enzyme, CYP2S1, in rats: Its regulation by aryl hydrocarbon receptor agonists

In the present study, we examined the expression of CYP2S1 mRNA and protein in tissues from male and female rats and investigated aryl hydrocarbon receptor (AhR)-mediated regulation. CYP2S1 mRNA was detected by RT-PCR in all rat tissues examined, except for the adrenal gland, and no sex-dependent differences were observed. To study the regulation of CYP2S1 mRNA expression by AhR agonists, rats were treated with 3-methylcholanthrene (3-MC; 25 mg/kg/day × 3 days) or with a single intraperitoneal injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at various dosages (0, 1, 5, 10, 50, 100 μg/kg). CYP2S1 mRNA levels were increased in lung, stomach, jejunum and ileum following treatment with 3-MC and in lung, liver and kidney tissues following treatment with TCDD. Induction of CYP2S1 mRNA was greater with TCDD than 3-MC treatment and was more pronounced in lung than other tissues. Antiserum raised against a peptide corresponding to the C-terminus of CYP2S1 was used to measure relative CYP2S1 protein expression by immunoblot analysis. An immunoreactive CYP2S1 protein band with an approximate molecular weight of 50 kDa was detected in microsomes of rat lung, stomach and kidney, but not other tissues. Unlike CYP2S1 mRNA, CYP2S1 protein levels were not increased after treatment with 3-MC or the highest dosage of TCDD, indicating that CYP2S1 protein expression was less sensitive than mRNA expression to AhR-mediated regulation. Our study is the first to characterize CYP2S1 mRNA and protein expression in rats, and from the results obtained, we conclude that AhR is involved in the transcriptional regulation of CYP2S1 in rats.