小鼠胚胎干细胞分化心肌细胞毒蕈碱受体的表达特征

为了探讨胚胎干细胞分化心肌细胞（ESCM）毒蕈碱受体的表达规律及β肾上腺素能系统对M2受体表达的影响，采用10^－4 mol/L维生素C体外诱导小鼠M13胚胎干细胞分化为心肌细胞，用RT-PCR检测到分化后的细胞表达心肌细胞特异性基因Nkx2.5和β肌球蛋白重链；用免疫荧光法检测到分化后的细胞表达心肌细胞特异性标志物α辅肌动蛋白.小鼠胚胎干细胞分化前表达M₁和M₂毒蕈碱受体，在分化过程中，M₁受体表达逐渐下降， M₂受体表达在第3 d显著下降，此后表达逐渐增加，在第14 d达到高峰；Western印迹结果显示，异丙肾上腺素明显抑制M₂受体的表达，选择性β₁肾上腺素受体拮抗剂CGP20712A明显上调其表达，而选择性β₂肾上腺素受体拮抗剂 ICI118551对其表达无影响.本实验表明，小鼠胚胎干细胞分化心肌细胞表达毒蕈碱受体, β肾上腺素能系统对M₂受体表达有调控作用.

Expression Pattern of Muscarinic Receptors in Mouse Embryonic Stem Cell-derived Cardiomyocytes

To investigate the expression pattern of muscarinic receptors in cardiomyocytes derived from embryonic stem cells (ESCM) and β adrenergic modulation of M₂ muscarinic receptor, the M13 mouse ES cells were induced by 10^－4 mol/L vitamin C to differentiate into cardiomyocytes. RT PCR revealed that cardiac specific genes, Nkx2.5 and β myosin heavy chain, expressed in the differentiated cells. By immunofluorescent technique, the expression of cardiac specific marker α actinin was found in the differentiated cells. M₁ and M₂ muscarinic receptors expressed in the undifferentiated ES cells. During the process of differentiation, the expression of M₁ receptor decreased gradually, while the expression of M2 receptor decreased significantly at differentiation day 3 and then increased, and reached the maximal level at differentiation day 14. Western blotting showed that isoprenaline inhibited the expression of M₂ receptor and CGP20712A (a selective β₁ adrenergic receptor antagonist) up regulated the expression, whereas ICI118551 (a selective β₂ adrenergic receptor antagonist) had no effects. These results revealed that muscarinic receptors differentially expressed in ESCM and β adrenergic systems modulated the expression of M₂ receptor.