Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells.
Magnesium sulfate inhibits the oxytocin-induced production of inositol 1,4,5-trisphosphate in cultured human myometrial cells.
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DOI：
10.1067/mob.2002.123897
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发表时间：
2002-08
影响因子：
9.8
通讯作者：
W. Hurd;V. Natarajan;J. Fischer;Dawn M. Singh;Shawn G Gibbs;V. Fomin
中科院分区：
文献类型：
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作者：
W. Hurd;V. Natarajan;J. Fischer;Dawn M. Singh;Shawn G Gibbs;V. Fomin
目的探讨硫酸镁对三磷酸肌醇生产的影响及其作用机制。研究设计：子宫肌层取自足月临产前剖宫产妇女。原代培养的子宫肌细胞经催产素、氟化钠或Bay K8644刺激后，加或不加硫酸镁或硝苯地平，测定三磷酸肌醇的含量。实验在含钙或无钙的含蛋氨酸的培养液中进行，并与细胞内钙离子螯合剂BAPTA-乙酰氧甲酯预先孵育。放射受体测定法测定三磷酸肌醇的产量。在单独的实验中，使用Fura-2和荧光分光光度法测量细胞内钙离子浓度([Ca(2+)](I))的变化。结果催产素、氟化钠和BAY K8644使三磷酸肌醇产量增加2~4倍。用硫酸镁(3×10~(-3)m o l/L)预先孵育5分钟后，无论在含钙或无钙的培养液中，催产素、氟化钠和Bay K8644诱导的三磷酸肌醇产量均显著降低。在无钙条件下，BAPTA-乙酰氧甲酯可使催产素刺激的三磷酸肌醇产量降低78%，并可完全阻止催产素的反应。在含钙条件下，硫酸镁可降低三磷酸肌醇的产量，而在无钙条件下，硫酸镁对三磷酸肌醇的产量无明显影响。无论在含钙或无钙介质中，催产素和BAY K 8644均可增加[Ca(2+)](I)，而硫酸镁均可降低[Ca(2+)](I)。结论硫酸镁通过直接作用于磷脂酶C，从而抑制4，5-二磷酸-磷脂酰肌醇-4，5-二磷酸特异性磷脂酶C的活性和随后的钙释放。
OBJECTIVE The purpose of this study was to determine the effects of magnesium sulfate on inositol trisphosphate production and the mechanism of these effects. STUDY DESIGN Myometrium was obtained at the time of cesarean delivery from women before labor at term. Inositol trisphosphate was measured in the primary myometrial cell cultures after stimulation with oxytocin, sodium fluoride, or Bay K 8644 with or without preincubation with magnesium sulfate or nifedipine. Experiments were performed in either calcium-containing or calcium-free medium that contained egtazic acid and after preincubation with the intracellular calcium chelator BAPTA-acetoxymethylester. Inositol trisphosphate production was measured by radioreceptor assay. In separate experiments, changes in intracellular calcium concentrations ([Ca(2+)](i)) were measured with the use of Fura-2 and spectrophotofluorometry. RESULTS Oxytocin, sodium fluoride, and Bay K 8644 increased inositol trisphosphate production 2- to 4-fold. Preincubation with magnesium sulfate (3 x 10(-3) mol/L) for > or = 5 minutes decreased oxytocin-, sodium fluoride-, and Bay K 8644-induced inositol trisphosphate production in either calcium-containing or calcium-free media. Preincubation with BAPTA-acetoxymethylester decreased oxytocin-stimulated inositol trisphosphate production by 78% in calcium-containing media and completely prevented the oxytocin response in calcium-free media. Magnesium sulfate decreased inositol trisphosphate production in calcium-containing media but had no additional effect in calcium-free media. Oxytocin and Bay K 8644 increased [Ca(2+)](i) in either calcium-containing or calcium-free media, and magnesium sulfate reduced this in both cases. CONCLUSION Magnesium sulfate appears to inhibit phosphatidylinositol-4, 5-bisphosphate-specific phospholipase C activity and subsequent calcium release in cultured myometrial cells by a direct effect on phospholipase C.