Lobaccaro-Henri C, Descomps B, Thaler-Dao H
Centre de Recherche INSERM, Montpellier, France.
J Steroid Biochem Mol Biol. 1996 Sep;59(1):63-73. doi: 10.1016/s0960-0760(96)00091-x.
We previously demonstrated that the antiprogestogen RU 486, when superfused on myometrial strips, induces a rapid decrease in spontaneous uterine contractile frequency, an increase in amplitude and duration of contractions, and a concomitant decrease in 6-keto PGF(1alpha) release. In this study, we present further work on the role of calcium transients and the involvement of the PLC/PKC pathway in mediating RU 486 effects. We found no clear causal relationship between the spontaneous contractility controlled by external Ca++ concentration and 6-keto PGF(1alpha) release depending mostly on intracellular Ca++ mobilization. We show that RU 486 strengthened the inhibitory effect of TMB8, a potent inhibitor of internal calcium, on both spontaneous contractility and 6-keto PGF(1alpha), release and antagonized the stimulatory action of thapsigargin, a toxin blocking the endoplasmic reticulum calcium pump (ER Ca++ ATPase). These data indicate that RU 486 could act as an inhibitor of intracellular Ca++ mobilization. A slight but significant decrease of the prostanoid liberation was observed in the presence of U73122, an inhibitor of PLC, but not in the presence of neomycin, another PLC inhibitory compound. PKC inhibitors, staurosporine and H7 did not significantly affect spontaneous 6-keto PGF1alpha release, showing that PIP2 hydrolysis and PKC pathway were not involved in the basal release of the prostacyclin metabolite. Vasopressin (AVP), an agent known to induce contractility of the non-pregnant human uterus, markedly increased 6-keto PGF(1alpha) release in a dose-dependent manner. Stimulation of GTP-regulated proteins (G proteins) by ALF4 was accompanied by a rise in 6-keto PGF(1alpha) liberation and a high contractile activity. The effects of both vasopressin and ALF4- were not significantly opposed by RU 486, indicating that other sources of Ca++, not controlled by the steroid, were involved in the agonist-stimulated prostanoid release. Studies with structurally related RU 486 analogues showed that the steroid effects were not dependent on their antihormonal activity, but rather on a specific 11beta arylsubstitution and a 17beta-hydroxy-13beta-methyl configuration of the 4,9-estradien-3-one molecule.
我们之前证明，抗孕激素RU 486在子宫肌条上进行灌流时，会使子宫自发收缩频率迅速降低，收缩幅度和持续时间增加，同时6-酮-前列腺素F(1α)释放减少。在本研究中，我们进一步探讨了钙瞬变的作用以及磷脂酶C/蛋白激酶C（PLC/PKC）途径在介导RU 486作用中的参与情况。我们发现，由细胞外Ca++浓度控制的自发收缩性与主要依赖细胞内Ca++动员的6-酮-前列腺素F(1α)释放之间没有明确的因果关系。我们表明，RU 486增强了内部钙的强效抑制剂TMB8对自发收缩性和6-酮-前列腺素F(1α)释放的抑制作用，并拮抗了毒胡萝卜素（一种阻断内质网钙泵（ER Ca++ ATP酶）的毒素）的刺激作用。这些数据表明，RU486可能作为细胞内Ca++动员的抑制剂。在存在PLC抑制剂U73122的情况下，观察到类前列腺素释放略有但显著降低，但在存在另一种PLC抑制化合物新霉素的情况下则未观察到。PKC抑制剂星形孢菌素和H7对自发的6-酮-前列腺素F1α释放没有显著影响，表明磷脂酰肌醇-4,5-二磷酸（PIP2）水解和PKC途径不参与前列环素代谢物的基础释放。血管加压素（AVP）是一种已知可诱导未孕人子宫收缩的物质，它以剂量依赖的方式显著增加6-酮-前列腺素F(1α)释放。ALF4对GTP调节蛋白（G蛋白）的刺激伴随着6-酮-前列腺素F(1α)释放的增加和高收缩活性。RU 486对血管加压素和ALF4的作用均无显著拮抗作用，表明类固醇未控制的其他Ca++来源参与了激动剂刺激的类前列腺素释放。对结构相关的RU 486类似物的研究表明，类固醇的作用不依赖于它们的抗激素活性，而是依赖于4,9-雌二烯-3-酮分子特定的11β芳基取代和17β-羟基-13β-甲基构型。
