Abayasekara D R, Michael A E, Webley G E, Flint A P
Institute of Zoology, Zoological Society of London, Regent's Park, UK.
Mol Cell Endocrinol. 1993 Nov;97(1-2):81-91. doi: 10.1016/0303-7207(93)90213-4.
It is well documented that prostaglandin F2 alpha (PGF2 alpha) inhibits progesterone production in luteal cells, but its mode of action is uncertain. It has recently been suggested that PGF2 alpha acts by activating the calcium and phospholipid-dependent protein kinase, protein kinase C (PKC). This hypothesis has been tested by comparing the site and mode of action of PGF2 alpha, a PGF2 alpha analogue (cloprostenol) and the PKC activator phorbol myristate acetate (4 beta PMA) in human granulosa-lutein cells. PGF2 alpha and cloprostenol exerted similar concentration-dependent inhibitory actions on gonadotrophin-stimulated cyclic AMP (cAMP) accumulation and progesterone production by human granulosa-lutein cells. The similarity in the actions of PGF2 alpha and cloprostenol in human granulosa-lutein cells suggests that they can be used interchangeably to study the role of PGF2 alpha in the regulation of steroidogenesis in the human ovary. Gonadotrophin-stimulated cAMP accumulation and progesterone production was also concentration-dependently inhibited by 4 beta PMA. In addition, cloprostenol and 4 beta PMA also inhibited dibutyryl cAMP-stimulated progesterone production, suggesting that these compounds inhibit LH action at sites before and after the generation of cAMP. The pre-cAMP site of action can be localised to the stimulatory G-protein (Gs) as both compounds inhibited cholera toxin-stimulated cAMP accumulation without affecting forskolin-stimulated cAMP accumulation. The post cAMP site of action can be localised to actions on cholesterol side chain cleavage enzyme, as both cloprostenol and 4 beta PMA inhibited 22R hydroxycholesterol-supported progesterone production without affecting pregnenolone-supported progesterone production. The finding that cloprostenol and 4 beta PMA interact with the steroidogenic cascade in a similar manner is indicative of a shared common mediator of their actions in human granulosa-lutein cells, i.e. PKC. The inhibitory actions of PGF2 alpha and 4 beta PMA on hLH-stimulated progesterone production were abolished in the presence of the PKC inhibitor, staurosporine. In addition, in PKC-depleted cells (achieved by exposure to 4 beta PMA for 20 h) the inhibitory actions of PGF2 alpha and 4 beta PMA were abolished. These results support the hypothesis that the inhibitory actions of PGF2 alpha are mediated by PKC in human granulosa-lutein cells.
已有充分文献证明，前列腺素F2α（PGF2α）可抑制黄体细胞中孕酮的产生，但其作用方式尚不确定。最近有人提出，PGF2α通过激活钙和磷脂依赖性蛋白激酶，即蛋白激酶C（PKC）发挥作用。通过比较PGF2α、一种PGF2α类似物（氯前列醇）和PKC激活剂佛波酯肉豆蔻酸酯（4βPMA）在人颗粒黄体细胞中的作用位点和作用方式，对这一假说进行了验证。PGF2α和氯前列醇对人颗粒黄体细胞中促性腺激素刺激的环磷酸腺苷（cAMP）积累和孕酮产生具有相似的浓度依赖性抑制作用。PGF2α和氯前列醇在人颗粒黄体细胞中的作用相似，这表明它们可互换使用，以研究PGF2α在人类卵巢类固醇生成调节中的作用。促性腺激素刺激的cAMP积累和孕酮产生也受到4βPMA的浓度依赖性抑制。此外，氯前列醇和4βPMA还抑制二丁酰cAMP刺激的孕酮产生，这表明这些化合物在cAMP产生之前和之后的位点抑制促黄体生成素（LH）的作用。cAMP产生前的作用位点可定位于刺激性G蛋白（Gs），因为这两种化合物均抑制霍乱毒素刺激的cAMP积累，而不影响福斯高林刺激的cAMP积累。cAMP产生后的作用位点可定位于对胆固醇侧链裂解酶的作用，因为氯前列醇和4βPMA均抑制22R羟基胆固醇支持的孕酮产生，而不影响孕烯醇酮支持的孕酮产生。氯前列醇和4βPMA以相似方式与类固醇生成级联反应相互作用的发现表明，它们在人颗粒黄体细胞中的作用存在共同的介质，即PKC。在PKC抑制剂星形孢菌素存在的情况下，PGF2α和4βPMA对人促黄体生成素（hLH）刺激的孕酮产生的抑制作用被消除。此外，在PKC耗竭的细胞中（通过暴露于4βPMA 20小时实现），PGF2α和4βPMA的抑制作用也被消除。这些结果支持了PGF2α的抑制作用在人颗粒黄体细胞中由PKC介导的假说。
