Serres C, Yang J, Jouannet P
Laboratoire d'Histologie-Embryologie, Université Paris XI, Centre Hospitalier, Le Kremlin-Bicetre, France.
Biochem Biophys Res Commun. 1994 Nov 15;204(3):1009-15. doi: 10.1006/bbrc.1994.2563.
RU486 decreases the intracellular free calcium concentration in human spermatozoa incubated in capacitation medium. We investigated the calcium fluxes that this progesterone antagonist acts on. We found that 10(-5) M RU486 slowed down the basal calcium influx while progesterone accelerated it. Moreover, in the same way as RU486 inhibits the calcium increase promoted by progesterone, it inhibited the calcium influx stimulated by 10(-6) M thapsigargin, an endoplasmic reticulum Ca(2+)-ATPase inhibitor. So we speculated that RU486 does not necessarily compete for the same binding sites as progesterone to exert its inhibitory action. In the absence of extracellular calcium, pretreatment by 10(-5) M RU486 decreased the peak of [Ca2+]i released by 5 microM ionomycin. This indicates that RU486 could also act at the membrane level of some intracellular organelles of calcium storage.
RU486可降低在获能培养基中孵育的人类精子细胞内的游离钙浓度。我们研究了这种孕酮拮抗剂作用的钙通量。我们发现，10(-5)M的RU486减缓了基础钙内流，而孕酮则加速了它。此外，与RU486抑制孕酮促进的钙增加的方式相同，它也抑制了由10(-6)M毒胡萝卜素（一种内质网Ca(2+)-ATP酶抑制剂）刺激的钙内流。因此我们推测，RU486不一定与孕酮竞争相同的结合位点来发挥其抑制作用。在无细胞外钙的情况下，用10(-5)M的RU486预处理可降低由5微摩尔离子霉素释放的[Ca2+]i峰值。这表明RU486也可能作用于某些钙储存细胞器的膜水平。
