Objectives To study the effects of DEHP and its main metabolite mono (2-ethylhexyl) phthalate (MEHP) exposure on steroidogenesis in MLTC-1.

Methods MLTC-1 were exposed to DEHP (0, 1, 10, 100, 1 000 μmol/L) and MEHP (0, 1, 10, 100, 1 000 μmol/L) for 24 h respectively. Apoptosis was detected by Annexin V/PI double staining, and real time quantitative RT-PCR method was conducted to explore the mRNA expression levels of the key enzymes involved in the synthesis of steroid hormones.

Results Apoptosis result showed 100 and 1 000 μmol/L DEHP and MEHP significantly induced the late apoptosis of MLTC-1, 1 000 μmol/L DEHP and MEHP significantly reduced the cell viability. Therefore, the lower concentrations of DEHP and MEHP were selected to evaluate the effect of DEHP and MEHP on the steroid synthesis pathway of MLTC-1 in the present study. RT-PCR result showed 1 μmol/L DEHP significantly increased the mRNA expression level of CYP17A1, while 100 μmol/L DEHP significantly inhibited mRNA expression level of CYP17A1, CYP11A1, key regulatory factor (SF-1). 10 μmol/L DEHP significantly increased the expression level of CYP1A1. 100 μmol/L DEHP significantly inhibited the expression of LHR. 1 μmol/L MEHP significantly increased the expression of 3β-HSD. However, MEHP had no significant effect on the expression of some enzymes such as STAR, CYP17A1, CYP11A1, insulin-like hormone 3 (INSL-3), SF-1, AR and LHR.

Conclusions DEHP and MEHP promoted MLTC-1 apoptosis and affected the expression of key genes in steroid hormone synthesis of MLTC-1, which may cause endocrine disruption.