Davis B J, Weaver R, Gaines L J, Heindel J J
Department of Microbiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Toxicol Appl Pharmacol. 1994 Oct;128(2):224-8. doi: 10.1006/taap.1994.1201.
Di-(2-ethylhexyl) phthalate (DEHP) exposure suppressed preovulatory granulosa cell estradiol production in adult cycling rats. The active metabolite of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), suppressed follicle-stimulating hormone (FSH)-stimulated cAMP and progesterone production in cultured rat granulosa cells. To examine how DEHP altered granulosa cell estradiol production, the effects of MEHP were studied in cultures of rat granulosa cells. Granulosa cells were obtained from DES-implanted 25-day-old female Fisher 344 rats and exposed in culture to various concentrations of MEHP (0 to 400 microM) in DMSO. Granulosa cells were stimulated with FSH, 8-bromo cyclic adenosine monophosphate (8br-cAMP), a stable cAMP analog, and various concentrations of testosterone. Estradiol production was measured by standard radioimmunoassays and normalized to cell protein. MEHP suppressed estradiol in a concentration-dependent manner whether granulosa cells were stimulated by FSH or 8-br cAMP. Therefore, MEHP suppressed estradiol independent of its suppression of the FSH-cAMP pathway and, thus, suppressed aromatase conversion of testosterone to estradiol. MEHP (100 microns) decreased the maximum velocity of aromatase in cells supplied with increasing concentrations of testosterone. However, MEHP did not alter the velocity or affinity of microsomal aromatase isolated from adult virgin Sprague-Dawley rat ovaries. Therefore, MEHP altered the absolute amount or availability of aromatase in granulosa cells. Decreased aromatase in granulosa cells would explain decreased estradiol concentrations from DEHP exposure in vivo.
邻苯二甲酸二（2-乙基己基）酯（DEHP）暴露可抑制成年发情周期大鼠排卵前颗粒细胞雌二醇的产生。DEHP的活性代谢产物单（2-乙基己基）邻苯二甲酸酯（MEHP）可抑制培养的大鼠颗粒细胞中促卵泡激素（FSH）刺激的环磷酸腺苷（cAMP）和孕酮的产生。为了研究DEHP如何改变颗粒细胞雌二醇的产生，我们在大鼠颗粒细胞培养物中研究了MEHP的作用。颗粒细胞取自植入己烯雌酚的25日龄雌性Fisher 344大鼠，并在培养中暴露于二甲基亚砜（DMSO）中不同浓度的MEHP（0至400微摩尔）。用FSH、8-溴环磷酸腺苷（8br-cAMP，一种稳定的cAMP类似物）和不同浓度的睾酮刺激颗粒细胞。通过标准放射免疫测定法测量雌二醇的产生，并将其标准化为细胞蛋白。无论颗粒细胞是由FSH还是8-br cAMP刺激，MEHP均以浓度依赖性方式抑制雌二醇的产生。因此，MEHP抑制雌二醇的产生与其对FSH-cAMP途径的抑制无关，从而抑制了睾酮向雌二醇的芳香化酶转化。MEHP（100微摩尔）降低了在供应增加浓度睾酮的细胞中芳香化酶的最大速度。然而，MEHP并未改变从成年未交配的Sprague-Dawley大鼠卵巢分离的微粒体芳香化酶的速度或亲和力。因此，MEHP改变了颗粒细胞中芳香化酶的绝对量或可用性。颗粒细胞中芳香化酶的减少可以解释体内DEHP暴露导致的雌二醇浓度降低。
