Ohhashi T, Azuma T
Am J Physiol. 1982 Jan;242(1):C25-30. doi: 10.1152/ajpcell.1982.242.1.C25.
Dose-response relationships for Mg2+ in a Mg2+-free bathing solution were obtained with isolated canine femoral arteries. At concentrations less than 5 mM, relaxant responses appeared in the preparations. In a concentration range of 10-20 mM, however, every one of the preparations invariably showed dose-dependent contractions. The relaxant and contractile responses were induced by the action of Mg2+ per se but not by the hyperosmolarity associated with the addition of Mg2+. Neither response was affected by the drugs that inhibited the actions of catecholamine, acetylcholine, serotonin, or histamine. The contractile response was kept unchanged in Ca2+-free Locke's solution and was almost independent of environmental calcium concentrations ranging from 2.2 to 8.2 mM. The contractile response was not affected under the influence of Ca antagonists, verapamil, or Mn2+. The presence of Ba2+ or Sr2+ enhanced the relaxant response and dose dependently suppressed the contractile response. The contractile response was still evoked in smooth muscles that were in the state of K+ contracture. These results suggest the possibility that the contractile action of Mg2+ was mediated by a release of intracellular Ca2+ or exerted directly on the contractile machinery of arterial smooth muscle.
利用离体犬股动脉，在无镁的浴液中获得了镁离子的剂量 - 反应关系。在浓度低于5 mM时，制剂出现舒张反应。然而，在10 - 20 mM的浓度范围内，每个制剂都无一例外地表现出剂量依赖性收缩。舒张和收缩反应是由镁离子本身的作用引起的，而不是由添加镁离子相关的高渗性引起的。这两种反应均不受抑制儿茶酚胺、乙酰胆碱、5 - 羟色胺或组胺作用的药物影响。在无钙的洛克氏溶液中，收缩反应保持不变，并且几乎与2.2至8.2 mM范围内的环境钙浓度无关。收缩反应在钙拮抗剂、维拉帕米或锰离子的影响下不受影响。钡离子或锶离子的存在增强了舒张反应，并剂量依赖性地抑制了收缩反应。在处于钾离子挛缩状态的平滑肌中仍可诱发收缩反应。这些结果提示，镁离子的收缩作用可能是通过细胞内钙离子的释放介导的，或者是直接作用于动脉平滑肌的收缩机制。
