Acetylcholine reversal of isoproterenol-stimulated sodium currents in rabbit ventricular myocytes.
Acetylcholine reversal of isoproterenol-stimulated sodium currents in rabbit ventricular myocytes.
复制标题
乙酰胆碱逆转兔心室肌细胞中异丙肾上腺素刺激的钠电流。
DOI：
10.1161/01.res.72.3.517
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发表时间：
1993
影响因子：
20.1
通讯作者：
Shibata,EF
中科院分区：
文献类型：
--
作者：
Matsuda,JJ;Lee,HC;Shibata,EF
我们最近发现β-肾上腺素能激动剂通过双重G蛋白调节途径增强兔心脏钠电流（INa）。为了确定是否毒蕈碱胆碱能受体刺激也可以调节INa，我们研究了乙酰胆碱（ACh）和卡巴胆碱对酶分散的兔心室肌细胞INa的影响。在室温下使用20 mM [Na+]o进行的全细胞膜片钳实验表明，100 nM异丙肾上腺素增加INa并加速电流衰减，如前所述。ACh（1 μ M）或卡巴胆碱（1 μ M）在整个INa激活范围内的测试电位和负保持电位至-80 mV时显著逆转了异丙肾上腺素的刺激作用。阿托品（1 μ M）可完全抑制这种作用，并通过研究细胞贴附贴片的单通道INa证实。当INa被毛喉素（1 μ M）刺激时，卡巴胆碱（1 μ M）显著逆转了这种作用。百日咳毒素（0.1或1.0 μ g/ml）孵育（12-15小时）可抑制毒蕈碱介导的INa抑制作用，表明该作用是抑制性G蛋白依赖性的。ACh抑制机制的进一步研究表明，ACh单独对INa没有影响，当细胞用cAMP（5 μ M）透析时，ACh不能抑制INa。此外，cGMP不能抑制异丙肾上腺素对INa的作用。这些数据表明，ACh的行为或接近腺苷酸环化酶刺激。因此，兔心脏Na+通道由毒蕈碱激动剂以类似于心脏Ca 2+通道的方式调节。
We have recently shown that beta-adrenergic agonists enhance the cardiac sodium current (INa) in rabbits through dual G-protein regulatory pathways. To determine if muscarinic cholinergic receptor stimulation can also modulate INa, we studied the effects of acetylcholine (ACh) and carbachol on INa in enzymatically dispersed rabbit ventricular myocytes. Whole-cell patch-clamp experiments done at room temperature using 20 mM [Na+]o showed that 100 nM isoproterenol increased INa and accelerated current decay as previously described. ACh (1 microM) or carbachol (1 microM) significantly reversed the stimulatory isoproterenol effects at test potentials throughout the INa activation range and at holding potentials negative to -80 mV. This effect was completely inhibited by atropine (1 microM) and was confirmed by studying single-channel INa from cell-attached patches. When INa was stimulated by forskolin (1 microM), carbachol (1 microM) significantly reversed the effect. The muscarinic-mediated inhibition of INa was inhibited by pertussis toxin (0.1 or 1.0 microgram/ml) incubation (12-15 hours), suggesting that the effect was inhibitory G-protein dependent. Further investigation of the ACh inhibitory mechanism revealed that ACh alone had no effect on INa and that when cells were dialyzed with cAMP (5 microM), ACh failed to inhibit INa. Furthermore, cGMP failed to inhibit the effect of isoproterenol on INa. These data suggest that ACh acts at or proximal to adenylate cyclase stimulation. Thus, rabbit cardiac Na+ channels are regulated by muscarinic agonists in a fashion similar to cardiac Ca2+ channels.