ERK1/2通路参与ET_A和ET_B受体介导的离体肠系膜上动脉收缩研究

目的探讨细胞外信号调节激酶1/2(ERK1/2)信号转导通路在内皮素1(ET-1)的两个G蛋白偶联受体ET_A和ET_B介导的收缩机制。方法用大鼠肠系膜上动脉器官培养模型,以敏感的离体药理学实验方法记录培养前后血管平滑肌张力,实时定量的PCR测定培养前后受体mRNA表达水平的变化。结果S6c不引起新鲜的肠系膜上动脉收缩,培养后ETB受体mRNA表达水平上调,介导的收缩明显增强(P<005);而ETA受体介导的收缩功能和mRNA均变化不大。低浓度的SB386023(10-5mol·L-1)降低S6c引起的最大收缩(Emax从239%±26%降至89%±13%,P<001),而对ET1引起的最大收缩并无影响(Emax271%±19%vs251%±16%,P>005);高浓度的SB386023(10-4mol·L-1)明显抑制ETA受体介导的收缩。结论ET-1通过ET_A受体介导新鲜动脉的收缩;动脉培养后表达ET_B受体;ERK1/2信号转导通路对ET_B受体的作用强于ET_A受体。

3Involvement of ERK1/2 pathway in endothelin ETA and ETB receptor-mediated contraction in isolated rat mesenteric artery

Aim To determine the involvement of extracellular signal-regulated kinase 1/2 pathway in endothelin (ET) receptor type A (ET_A) and B (ET_B)-mediated contraction.Mehtods The specific inhibitor for ERK1/2 pathway SB386023 was used to define the intracellular pathway for ET-1 (agonist for both ET_A and ET_B) and sarafotoxin 6c (S6c) (selective agonist for ET_B) induced contraction in isolated rat mesenteric arteries. The contraction was recorded by sensitive in vitro pharmacology system and the receptors mRNA was quantified by a real-time PCR.Results S6c did not induce contraction in fresh mesenteric artery while after organ culture of the artery for 24 h there was strong contractile response to S6c parallel with increase of mRNA for ET_B receptor. However, ET_A receptor-mediated contraction and mRNA for ET_A receptor did not markedly change after organ culture of the artery. Low concentration of SB386023 (10~-5 mol·L~-1 ) significantly reduce S6c-evoked contraction with Emax decreased from 239%±26% to 89%±13%,(P<0.01) while higher concentration of SB386023 (10~-4 mol·L~-1 ) was required to reduce ET_A receptor-mediated contraction to the same degree. Conclusion The present study revealed that ET-1 acted via ET_A receptor in fresh mesenteic artery and organ culture resulted in up-regulated ET_B receptor expression and enhanced contractile response to S6c. ERK1/2 pathway plays more important role on ET_B receptor-mediated contraction than on ET_A receptor-mediated contraction.