Treinen K A, Heindel J J
Developmental and Reproductive Toxicology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina.
Reprod Toxicol. 1992;6(2):143-8. doi: 10.1016/0890-6238(92)90116-b.
We have recently shown that mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of the reproductive toxicant di-(ethylhexyl) phthalate (DEHP), inhibited FSH- but not forskolin-, isoproterenol-, or cholera toxin-stimulated granulosa cell cAMP accumulation in vitro. In addition, MEHP also inhibited FSH-stimulated progesterone production, a cAMP-dependent process. Similar to MEHP, the protein kinase C (PKC) activator, 12-0-tetradecanoyl-phorbol 13-acetate (TPA) has been shown to inhibit rat granulosa cell cAMP accumulation in a FSH-specific manner, and decrease FSH-stimulated progesterone production. Due to the similarity with respect to inhibition of cAMP accumulation, we conducted studies to determine if the inhibitory actions of MEHP on granulosa cell function are mediated via activation of PKC. Treatment of granulosa cells for 48 h with 100 microM MEHP produced no effect on forskolin- or isoproterenol-stimulated progesterone production, indicating that MEHP does not have a post-cyclic AMP site of action with respect to progesterone inhibition. Unlike the FSH-specific effect seen with MEHP, treatment with 10 nM TPA inhibited FSH-, forskolin-, and isoproterenol-stimulated progesterone production. In addition, maximally inhibitory concentrations of TPA and MEHP caused significantly greater inhibition of FSH-stimulated cAMP accumulation than either compound alone. Finally, addition of the progesterone precursor, pregnenolone, reversed the FSH-stimulated progesterone production inhibition by MEHP, but not that by TPA. Taken together, these data indicate that the inhibitory effects of MEHP on granulosa cell function are independent of phorbol ester-sensitive PKC activation.
我们最近发现，生殖毒物邻苯二甲酸二（2-乙基己基）酯（DEHP）的活性代谢物单-（2-乙基己基）邻苯二甲酸酯（MEHP），在体外可抑制促卵泡激素（FSH）刺激的颗粒细胞环磷酸腺苷（cAMP）积累，但对福斯高林、异丙肾上腺素或霍乱毒素刺激的颗粒细胞cAMP积累无抑制作用。此外，MEHP还抑制FSH刺激的孕酮生成，这是一个依赖cAMP的过程。与MEHP类似，蛋白激酶C（PKC）激活剂12-0-十四烷酰佛波醇-13-乙酸酯（TPA）已被证明以FSH特异性方式抑制大鼠颗粒细胞cAMP积累，并降低FSH刺激的孕酮生成。由于在抑制cAMP积累方面存在相似性，我们进行了研究以确定MEHP对颗粒细胞功能的抑制作用是否通过PKC激活介导。用100微摩尔/升MEHP处理颗粒细胞48小时，对福斯高林或异丙肾上腺素刺激的孕酮生成没有影响，这表明MEHP在孕酮抑制方面没有作用于环磷酸腺苷后的作用位点。与MEHP所见的FSH特异性作用不同，用10纳摩尔/升TPA处理可抑制FSH、福斯高林和异丙肾上腺素刺激的孕酮生成。此外，TPA和MEHP的最大抑制浓度对FSH刺激的cAMP积累的抑制作用明显大于单独使用任何一种化合物。最后，添加孕酮前体孕烯醇酮可逆转MEHP对FSH刺激的孕酮生成的抑制作用，但不能逆转TPA的抑制作用。综上所述，这些数据表明MEHP对颗粒细胞功能的抑制作用独立于佛波酯敏感的PKC激活。
