ERKs及细胞内游离钙在内皮素-1诱导心肌细胞肥大反应中的作用

Roles of ERKs and intracellular free calcium in cardiomyocyte hypertrophic response induced by endothelin-1

目的 :研究细胞外信号调节激酶 (ERKs)及细胞内游离钙 ([Ca2 + ]i)在内皮素 - 1 (ET - 1 )介导心肌细胞肥大反应中的作用及机制。方法 :利用培养的新生大鼠心肌细胞 ,①以蛋白合成速率、蛋白含量及细胞表面积为心肌肥大反应的指标 ;②用滤纸法测定ERKs活性 ;③用Fura - 2 /AM作为钙荧光指示剂测定心肌 [Ca2 + ]i浓度。结果 :①ET - 1浓度依赖性增加新生大鼠心肌细胞蛋白质含量和心肌细胞表面积、ERKs活性及 [Ca2 + ]i浓度 ,以上作用可被ETA 受体拮抗剂BQ1 2 3所完全抑制 ,被百日咳毒素 (PTX)部分抑制 ,而ETB 受体拮抗剂BQ788则无效 ;②ERKs激酶特异性抑制剂PD980 5 9可完全抑制ET - 1激活ERKs的作用 ,钙通道拮抗剂硝苯地平可明显抑制ET - 1介导的[Ca2 + ]i浓度增加 ,但二者皆仅部分抑制ET - 1介导的心肌细胞肥大反应 ;③蛋白激酶C(PKC)选择性抑制剂stau rosporine并不能明显抑制ET - 1介导的ERKs激活 ,但可抑制ET - 1介导的的 [Ca2 + ]i浓度增加及心肌细胞肥大反应。结论 :ET - 1主要通过ETA 受体并经PTX敏感的G -蛋白介导心肌细胞肥大反应 ,该作用至少涉及两条途径 :①通过PKC介导的心肌 [Ca2 + ]i浓度增加 ;②不通过PKC介导的ERKs激活。

AIM: To study the roles and mechanisms of ERKs and intracellular free calcium in cardiomyocyte hypertrophic response induced by endothelin-1(ET-1). METHODS: (1) Neonatal rat cardiomyocyte hypertrophic response was assayed by measuring cell surface area and protein content; (2) ERKs activity was determined by Whatman Paper Filter method; (3) Intracellular free calcium concentration ([Ca 2+ ]i) was measured using Fura-2/AM as a fluorescent indicator. RESULTS: (1) ET-1 could increase total protein production, surface area, ERKs activity and [Ca 2+ ]i in cultured cardiomyocyte in dose-dependent manner at concentrations ranging from 10 -9 to 10 -7 mol/L. And this effect could be abolished by BQ123, an antagonist of ET A receptor, partly inhibited by PTX, but not by BQ788, an antagonist of ET B receptor.(2)The activation of ERKs and the increase of [Ca 2+ ]i induced by ET-1 were obviously inhibited by PD98059, a selective ERKs kinase inhibitor, and nifedipine, a calcium channel blocker, respectively. Both antagonists partially inhibited ET-1-stimulated cardiomyocyte hypertrophic response. (3) Staurosporine, a selective PKC inhibitor, could inhibit ET-1-stimulated cardiomyocyte hypertrophic response and increase of [Ca 2+ ]i, but not affect the activation of ERKs. CONCLUSION: Cardiomyocyte hypertrophic response induced by ET-1 is mediated by ET A receptor coupled to PTX-sensitive G-protein, which involves at least two signalling pathways: PKC-mediated increase of [Ca 2+ ]i , and PKC-independent activation of ERKs. [