Cytochrome P450 17α-hydroxylase (CYP17) and cytochrome P450 aromatase (CYP19) are key steroidogenic enzymes in androgen and estrogen synthesis. This study evaluated the effects of nonylphenol (NP) on CYP17 and CYP19 expression in the ovary of Sprague-Dawley rats. All female rats were administered orally with the vehicle (control, corn oil), diethylstilbestrol (DES, 5.0 μg/kg) and NP (50, 100, or 200 mg/kg/day), which was starting when they were weaned at 21 days of age for 20 days. Twenty four hours after final dose, the animals were anesthetized with ether. Significant decreases in the uterus (wet weight) were observed with 5.0 μg/kg/day DES (78% of control) and 200 mg/kg/day NP (62% of control), respectively. Additionally, ovarian weight was significantly decreased with 5.0 μg/kg/day DES (63% of control) and 200 mg/kg/day NP (72% of control). The serum estradiol levels were slightly lower in DES and high dose NP treatment groups, but the T4 levels were not affected by DES and NP. The expression of the ovarian CYP19 gene increased with low doses (50 and 100 mg/kg/day) of NP, while DES and high dose of NP (200 mg/kg/day) did not affect on the CYP19 mRNA levels. In contrast to the CYP19 gene, the CYP17 gene expression level was significantly down-regulated by the DES and 200 mg/kg/day NP. This result suggests that NP inhibits ovarian estrogen synthesis by suppressing CYP17 mRNA expression, and different mechanisms might exist for the expression of steroidogenic CYP17 and CYP19 genes in the ovary of Sprague-Dawley rats in response to NP.
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