Safety Research Laboratories, Dainippon Sumitomo Pharma Co., Ltd, Osaka, Japan.
J Toxicol Sci. 2012;37(3):483-90. doi: 10.2131/jts.37.483.
Mono-(2-ethylhexyl) phthalate (MEHP) is the most toxic metabolite of di-(2-ethylhexyl) phthalate (DEHP). It has been reported that DEHP causes abnormal reproductive development in women, and suppresses estradiol synthesis and ovulation in female rats with diminished size of preovulatory follicles. The present study was conducted to evaluate the ovarian toxicity of MEHP using cultured rat ovarian follicles. Secondary follicles were isolated from the ovaries of 14-day-old female rats and cultured for 48 hr with MEHP (0, 10, 30, and 100 µg/ml). At 0, 24, and 48 hr of MEHP treatment, follicular diameters were measured. After the culture, viability and apoptosis of follicles were assessed, and progesterone, androstenedione, testosterone, and estradiol levels in culture media were measured. At 100 µg/ml, suppression of follicular development was observed, which is associated with decreased viability of follicles and apoptosis of granulosa cells. At this concentration, progesterone level increased markedly, whereas androstenedione, testosterone, and estradiol levels decreased. At 10 and 30 µg/ml, follicular development was not suppressed, no apoptotic change was observed, and the levels of all measured steroid hormones tended to increase. The combined levels of all steroid hormones increased at all concentrations of MEHP, and the increase implies that MEHP activates the synthetic pathway from cholesterol to estradiol including de novo synthesis of cholesterol. However, the progesterone/androstenedione ratio increased extremely at 100 µg/ml, and the increase implies that MEHP inhibits the conversion of progesterone to androstenedione. In conclusion, MEHP induces ovarian toxicity via suppression of follicular development and abnormal steroid hormone synthesis in cultured rat ovarian follicles.
邻苯二甲酸二（2-乙基己基）酯（DEHP）的最毒代谢产物是单（2-乙基己基）邻苯二甲酸酯（MEHP）。据报道，DEHP 会导致女性生殖发育异常，并通过抑制雌性大鼠的雌二醇合成和排卵，导致成熟前卵泡体积减小。本研究采用培养的大鼠卵巢卵泡，评估 MEHP 的卵巢毒性。从 14 日龄雌性大鼠的卵巢中分离出次级卵泡，并用 MEHP（0、10、30 和 100μg/ml）培养 48 小时。在 MEHP 处理 0、24 和 48 小时时，测量卵泡直径。培养结束后，评估卵泡的活力和凋亡，并测量培养基中孕激素、雄烯二酮、睾酮和雌二醇的水平。在 100μg/ml 时，观察到卵泡发育受到抑制，这与卵泡活力降低和颗粒细胞凋亡有关。在该浓度下，孕激素水平显著增加，而雄烯二酮、睾酮和雌二醇水平降低。在 10 和 30μg/ml 时，卵泡发育未受抑制，未观察到凋亡变化，所有测量的类固醇激素水平均呈上升趋势。所有 MEHP 浓度下，所有类固醇激素的总水平均增加，表明 MEHP 激活了从胆固醇到雌二醇的合成途径，包括胆固醇的从头合成。然而，在 100μg/ml 时，孕激素/雄烯二酮比值极高增加，表明 MEHP 抑制了孕激素向雄烯二酮的转化。综上所述，MEHP 通过抑制培养大鼠卵巢卵泡的卵泡发育和异常类固醇激素合成，诱导卵巢毒性。
