CONTRASTING CELLULAR EFFECTS OF BETA1 AND BETA2 ADRENERGIC RECEPTOR STIMULATION

刺激β2肾上腺素能受体介导的机械效应是 在分离的大鼠心室肌细胞上进行了研究。β2-肾上腺素能受体 刺激由β2选择性激动剂Zinterol和 异丙肾上腺素(ISO)在β1选择性拮抗剂CGP-存在下的作用 20712A。ICI被用作选择性的β2-受体拮抗剂。津特罗尔有一个 明显的正性肌力作用，与增加 才是暂时性的。此外，在选择性β1存在的情况下，ISO- 阻滞剂CGP-20712A对收缩和血管紧张素转换酶的作用非常相似 转瞬即逝。Zint和ISO的作用均可被β2-受体拮抗。 阻滞剂ICI 118,551，但不是CGP。此外，两国的比较数据 β2与β1-肾上腺素能受体刺激显示有一些 细胞对β1和β2肾上腺素能反应的显著差异 刺激。对于给定水平的变力作用，β2受体 刺激对收缩的时间进程和CaI的影响较小 短暂性对肌丝钙离子的敏感性较小 比β1受体刺激更能诱发心律失常。这些结果表明 首次在大鼠心肌中发现β2-肾上腺素能受体的功能 与β1肾上腺素受体共存，提示cAMP通过 Beta 1和Beta 2可以被划分或者Beta 1被激活 抵消众所周知的cAMP依赖作用的细胞机制 收缩、一过性及对肌丝和肌丝的时间进程 精子质网对钙离子的反应性。

The mechanical effects mediated by beta 2-adrenoceptor stimulation were studied in isolated rat ventricular myocytes. Beta 2-adrenoceptor stimulation was induced by using beta 2-selective agonist Zinterol and isoproterenol (ISO) in the presence of beta 1-selective antagonist CGP- 20712A. ICI was used as a selective beta 2-antagonist. Zinterol has an apparent positive inotropic effect which was associated with an increase in Cai transient. In addition, ISO in the presence of selective beta 1- blocker CGP-20712A has very similar effects on contraction and Cai transient. Both the effect of Zint and ISO can be antagonized by beta 2- blocker ICI 118,551, but not by CGP. Furthermore, the comparative data of beta 2 vs. beta 1-adrenoceptor stimulation show that there are some striking differences of cell responses to beta 1 and beta 2-adrenergic stimulation. For a given level of inotropic effect, beta 2 receptor stimulation has less effects on the time course of contraction and Cai transient on the myofilament sensitivity to Ca i, and is less arrhythmogenic than beta 1 receptor stimulation. These results demonstrate for the first time that in rat myocardium beta 2-adrenoceptors functionally coexist with beta 1-adrenoceptors and suggest that the cAMP stimulation by beta 1 and beta 2 may be compartmentalized or that beta 1 activates cellular mechanisms that offset the well-known cAMP-dependent action on the time course of contraction, Cai transient and on myofilament and sacroplasmic reticulum responsiveness to Ca 2+.