Longo M, Jain V, Vedernikov Y P, Facchinetti F, Saade G R, Garfield R E
Department of Obstetrics and Gynecology, The University of Texas Medical Branch, Galveston, Texas 77555-1062, USA.
Am J Obstet Gynecol. 2001 Apr;184(5):971-8. doi: 10.1067/mob.2001.112587.
The aim of this study was to investigate the role of nitric oxide in the vasorelaxant effect of magnesium sulfate during pregnancy.
Segments of 3 mm of the aorta, with or without intact endothelium, from 16- or 22-day-pregnant rats were mounted in organ chambers with standard Krebs solution or low-magnesium Krebs solution for measurement of isometric tension. The rings were contracted with phenylephrine, and cumulative concentration-response curves for magnesium were determined after incubation with various inhibitors.
Magnesium relaxed the aortic rings from pregnant rats in a concentration-dependent manner. The relaxation was significantly lower on day 22 of gestation than on day 16 of gestation. Removal of the endothelium or incubation with 10(-4)-mol/L N omega-nitro-L -arginine methyl ester (a nitric oxide synthase inhibitor), 10(-5)-mol/L 6-anilino-5,8-quinolinedione (a guanylate cyclase inhibitor), or 10(-5)-mol/L indomethacin (a cyclooxygenase inhibitor) significantly decreased the relaxant effect of magnesium on aortic rings from 16-day-pregnant but not 22-day-pregnant rats. Treatment with minimally effective concentrations of a nitric oxide donor (3 x 10(-10)-mol/L sodium nitroprusside) or a cyclic guanosine monophosphate analog (10(-6)-mol/L 8-bromo-cyclic guanosine monophosphate) restored the response to magnesium.
The relaxant effect of magnesium on rat aortic rings was dependent on both endothelium and gestational age and was lower at term than during late pregnancy. The endothelium appears to potentiate the vasorelaxant effects of magnesium through the nitric oxide-cyclic guanosine monophosphate and cyclooxygenase systems.
本研究旨在探讨一氧化氮在孕期硫酸镁血管舒张作用中的作用。
将来自妊娠16天或22天大鼠的3毫米主动脉段（有或无完整内皮）置于装有标准 Krebs 溶液或低镁 Krebs 溶液的器官浴槽中，以测量等长张力。用去氧肾上腺素使血管环收缩，在用各种抑制剂孵育后测定硫酸镁的累积浓度 - 反应曲线。
硫酸镁以浓度依赖的方式使妊娠大鼠的主动脉环舒张。妊娠第22天的舒张作用明显低于妊娠第16天。去除内皮或用10(-4) - 摩尔/升 Nω - 硝基 - L - 精氨酸甲酯（一种一氧化氮合酶抑制剂）、10(-5) - 摩尔/升 6 - 苯胺基 - 5,8 - 喹啉二酮（一种鸟苷酸环化酶抑制剂）或10(-5) - 摩尔/升吲哚美辛（一种环氧化酶抑制剂）孵育，可显著降低硫酸镁对妊娠16天大鼠主动脉环的舒张作用，但对妊娠22天大鼠无效。用最低有效浓度的一氧化氮供体（3×10(-10) - 摩尔/升硝普钠）或环磷酸鸟苷类似物（10(-6) - 摩尔/升 8 - 溴 - 环磷酸鸟苷）处理可恢复对硫酸镁的反应。
硫酸镁对大鼠主动脉环的舒张作用依赖于内皮和妊娠年龄，足月时低于妊娠晚期。内皮似乎通过一氧化氮 - 环磷酸鸟苷和环氧化酶系统增强硫酸镁的血管舒张作用。
