丹酚酸B镁抑制ATP和KCl诱导大鼠主动脉平滑肌细胞内钙的升高

目的研究丹酚酸B镁(M agnesium lithosperm ate B,MLB)对去内皮离体血管舒缩反应以及对血管平滑肌细胞内游离钙浓度Ca2+]i的影响。方法去内皮大鼠胸主动脉血管环等张收缩实验和采用钙离子荧光指示剂F luo-3,运用F-4500阳离子测定系统动态检测胸主动脉平滑肌细胞Ca2+]i。结果血管舒缩实验显示,无钙或常钙条件下MLB对血管基础张力均无作用。MLB 50~200μmol.L-1预给药组抑制无钙条件下苯肾上腺素(PE)1μmol.L-1诱导的血管收缩以及常钙条件下KC l 60 mmol.L-1诱导的血管收缩,并呈浓度相关性。而钙离子通道阻滞剂维拉帕米(Ver)10μmol.L-1则完全阻断KC l诱导的血管收缩。在复钙实验中观察到,MLB 50~200μmol.L-1不仅抑制PE 1μmol.L-1诱导的内钙依赖性血管收缩,而且对复钙后外钙依赖性的血管收缩也有抑制作用。细胞内钙测定实验表明,MLB预孵育的AVSMCs静息态Ca2+]i没有变化。无钙条件下,MLB 50、100和200μmol.L-1抑制ATP20μmol.L-1诱导内钙释放引起的Ca2+]i升高,抑制率分别为17.4%、32.4%和61.1%,显示较好的浓度相关性。AVSMCs于常钙条件下用Thapsigargin耗竭钙库后,KCl 60 mmol.L-1诱发外钙内流,引起Ca2+]i升高,10μmol.L-1的Ver则能完全阻断这种外钙内流。在MLB预给药组,KCl诱导的Ca2+]i升高降低,抑制率分别为20.0%、32.8%和52.6%。结论MLB能够抑制PE、高K+和复Ca2+诱导的血管收缩,并能抑制ATP和KCl诱导的血管平滑肌细胞内钙的升高,提示MLB对血管平滑肌细胞内钙的影响可能与抑制细胞内钙释放和电压依赖性钙通道有关。

Magnesium lithospermate B inhibits intracellular calcium elevation induced by ATP and KCl in rat vascular smooth muscle cells

Aim To investigate the effects of magnesium lithospermate B(MLB) on vasoconstriction of denuded aortic rings in vitro,as well as the effects of MLB on cytosolic free calcium concentration(Ca~(2+)]_i) in aortic vascular smooth muscle cells(AVSMCs).Methods Isotonic tension was measured in the rat thoracic aortic rings without endothelium and quantitative changes of Ca~(2+)]_i were directly monitored in AVSMCs loaded with the fluorescent calcium indicator Fluo-3 using intracellular cation measurement system.Results MLB had no effects on resting ring tension in the presence or absence of extracellular Ca~(2+).In rings exposed to 50～200 μmol·L~(-1) MLB,the isotonic contractions induced by 1 μmol·L~(-1) PE were decreased in calcium-free K-H solution.However,in the presence of extracellular Ca~(2+),KCl 60 mmol·L~(-1) produced isotonic contractions that were abolished by verapamil 10 μmol·L~(-1) or inhibited by pretreatment of 50～200 μmol·L~(-1) MLB in a concentration-dependent manner.When administered to the rings precontracted with 1 μmol·L~(-1) PE in the absence of extracellular Ca~(2+),a second extracelluar-calcium-dependent vasoconstriction induced by restoration of extracellular Ca~(2+) was also reduced by pretreatment of 50～200 μmol·L~(-1) MLB.Moreover,MLB,at concentration of 50～200 μmol·L~(-1),produced little effect on AVSMCs Ca~(2+)]_i in the presence or absence of extracellular Ca~(2+).In AVSMCs exposed to 50～200 μmol·L~(-1) MLB,the inhibitory effects of MLB on Ca~(2+)]_i induced by 20 μmol·L~(-1) ATP were concentration-dependent,with decreases ranging from 17.4% to 61.1% in the absence of extracellular Ca~(2+).In the presence of extracellular Ca~(2+) and thapsigargin,the increases in AVSMCs Ca~(2+)]_i evoked by 60 mmol·L~(-1) KCl were inhibited by pretreatment with MLB(50～200 μmol·L~(-1)) or abolished by pretreatment with verapamil(10 μmol·L~(-1)).Conclusions MLB inhibits vasoconstriction induced by PE,high-K~+,and re-Ca~(2+).MLB also has inhibitory effects on increase of Ca~(2+)]_i induced by ATP and high K~+ in AVSMCs.These results indicate that both the blocking effects on calcium release and voltage-dependent calcium channels may be responsible for the effects of MLB on Ca~(2+)]_i in vascular smooth muscle cells.