Ogura Junko, Mitamura Mana, Someya Akiyoshi, Shimamura Ken, Takayama Hiromitsu, Aimi Norio, Horie Syunji, Murayama Toshihiko
Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan.
Eur J Pharmacol. 2004 Jan 12;483(2-3):139-46. doi: 10.1016/j.ejphar.2003.10.022.
Previously, we reported that mesaconitine, an aconite alkaloid, increased intracellular Ca(2+) concentration (Ca(2+)) level in endothelium and caused relaxation in rat aorta via nitric oxide production. In the present study, we investigated the mechanisms of increase in the Ca(2+) level induced by mesaconitine in rat aorta and in human umbilical vein endothelial cells (HUVECs). Treatment with the low Na(+) buffer delayed the 30 microM mesaconitine-, but not 10 microM acetylcholine-, induced relaxation in rat aorta. Treatments with an inhibitor of Na(+)/Ca(2+) exchangers (20 microM 3',4'-dichlorobenzamil) and a reversed mode (Ca(2+) influx) inhibitor of the exchangers (30 microM 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulfonate, KBR7943) showed similar effects. In HUVECs, 30 microM mesaconitine increased the Ca(2+) level in the presence of extracellular CaCl(2) and NaCl, and the response was inhibited by KBR7943. Mesaconitine increased intracellular Na(+) concentration level in HUVECs. The Ca(2+) response by mesaconitine was inhibited by 100 microM D-tubocurarine (an inhibitor of nicotinic acetylcholine receptors), but was not inhibited in the glucose-free buffer and by inhibitors of Na(+)/H(+) exchangers. These findings suggest that mesaconitine stimulated Ca(2+) influx via the Na(+)/Ca(2+) exchangers in endothelial cells and caused relaxation in the aorta. The possibility of D-tubocurarine-sensitive Na(+) channels as target(s) of mesaconitine is discussed.
此前，我们报道过乌头生物碱中乌头碱可增加内皮细胞内的钙离子浓度（[Ca(2+)]i）水平，并通过一氧化氮生成使大鼠主动脉舒张。在本研究中，我们探究了中乌头碱诱导大鼠主动脉和人脐静脉内皮细胞（HUVECs）内[Ca(2+)]i水平升高的机制。用低钠缓冲液处理可延迟30微摩尔中乌头碱诱导的大鼠主动脉舒张，但不影响10微摩尔乙酰胆碱诱导的舒张。用钠/钙交换体抑制剂（20微摩尔3',4'-二氯苯甲酰胺）和交换体反向模式（钙离子内流）抑制剂（30微摩尔2-[2-[4-(4-硝基苄氧基)phenyl]乙基]异硫脲甲磺酸盐，KBR7943）处理显示出类似效果。在HUVECs中，30微摩尔中乌头碱在细胞外存在氯化钙和氯化钠时可增加[Ca(2+)]i水平，且该反应被KBR7943抑制。中乌头碱可增加HUVECs内的细胞内钠离子浓度水平。中乌头碱引起的[Ca(2+)]i反应被100微摩尔D-筒箭毒碱（烟碱型乙酰胆碱受体抑制剂）抑制，但在无糖缓冲液中以及用钠/氢交换体抑制剂处理时未被抑制。这些发现表明中乌头碱通过内皮细胞中的钠/钙交换体刺激钙离子内流并导致主动脉舒张。还讨论了D-筒箭毒碱敏感的钠离子通道作为中乌头碱作用靶点的可能性。
