Abstract: OBJECTIVE:To study the effects of di-(2-ethylhexyl) phthalate (DEHP) on expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) in MCF-7 cells. METHODS:MCF-7 cells in cultured were exposed to DEHP in different doses (0.05,0.1,0.2,0.4,0.8 mmol/L) for 12,24,48 h,or to one dose (0.8 mmol/L) at different times (3,6,12,24,48 h). Expression of 3β-HSD mRNA was detected by real-time PCR,expression of 3β-HSD protein was detected by western blot. RESULTS:After treatment of MCF-7 cells with DEHP at 0.1-0.8 mmol/L for 12-48 h, expression levels of 3β-HSD mRNA were significantly higher than that of the control group (P < 0.01). Treatment with the lowest dose of DEHP treatment (0.05 mmol/L) for 48h also induced significant increase of 3β-HSD mRNA expression (P < 0.05). Our study also show a dose-effect relationship. Expression of 3β-HSD mRNA also showed time-dependent effects after treatment with 0.8 mmol/L DEHP for 6,12,24,48 h (P < 0.01). Expression of 3β-HSD protein was also higher after treatment with DEHP at doses of 0.2-0.8 mmol/L (P < 0.05 or P < 0.01). In the 0.4,0.8 mmol/L dose group,expression of 3β-HSD protein level increased gradually with the increasing doses (P < 0.05 or P < 0.01). CONCLUSION:DEHP induced up-regulation of 3β-HSD mRNA and protein. Our findings indicate that the mechanism of DEHP toxicity may be related to the induction of changes of 3β-HSD during steroid synthesis.

Key words: di-(2-ethylhexyl) phthalate, 3β-hydroxysteroid dehydrogenase, gene expression, reproductive toxicity