Genistein increases the sensitivity of cardiac ion channels to β-adrenergic receptor stimulation
Genistein increases the sensitivity of cardiac ion channels to β-adrenergic receptor stimulation
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DOI：
10.1161/01.res.83.1.33
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发表时间：
1998-07-13
影响因子：
20.1
通讯作者：
Harvey, RD
中科院分区：
文献类型：
--
作者：
Hool, LC;Middleton, LM;Harvey, RD
采用全细胞膜片钳技术监测酪氨酸激酶抑制剂金雀异黄素对离体豚鼠心室肌细胞记录的膜电流的影响。在对照条件下，金雀异黄素（50μmol/L）不会激活潜在的cAMP调节的Cl-电流（I-Cl）。然而，在存在亚阈值浓度（1 nmol/L）的 β-肾上腺素能激动剂异丙肾上腺素 (Iso) 时，金雀异黄素会导致该电流接近最大激活。在没有染料木黄酮的情况下，Iso 激活 I-Cl，EC50 为 5 nmol/L。在金雀异黄素存在下，Iso 激活 I-Cl，EC50 为 0.3 nmol/L。在黄豆苷元（50 μmol/L）存在时没有观察到这种促进作用，黄豆苷元是染料木黄酮的类似物，仅微弱地抑制酪氨酸激酶活性。此外，过氧钒酸盐是磷酸酪氨酸磷酸酶活性的有效抑制剂，可单独抑制 Iso 激活的 I-Cl，并在 Iso 存在的情况下阻断染料木黄酮的刺激作用。为了确定金雀异黄素的刺激作用是否对 I-Cl 具有特异性，我们还研究了它对这些细胞中存在的 cAMP 调节的延迟整流 K+ 电流 (I-K) 和 L 型 Ca2+ 电流 (ICa-L) 的作用。基础 I-K 和 ICa-L 被染料木黄酮部分（约 30% 至 40%）抑制。然而，黄豆苷元模仿了这种抑制作用，表明不涉及酪氨酸激酶活性的抑制。除了非特异性抑制作用外，金雀异黄素还导致未阻断的阳离子电流的β-肾上腺素能敏感性显着增加。在没有染料木黄酮的情况下，1 nmol/L Iso 对 I-K 或 ICa-L 没有影响。然而，在金雀异黄素存在的情况下，1 nmol/L Iso 显着增加了两种电流的强度。这些结果表明酪氨酸激酶活性可能在调节心脏β-肾上腺素能反应性中发挥重要作用。
The whole-cell patch-clamp technique was used to monitor the effects of genistein, a tyrosine kinase inhibitor, on membrane currents recorded from isolated guinea pig ventricular myocytes, Under control conditions, genistein (50 mu mol/L) did not activate the latent cAMP-regulated Cl- current (I-Cl). However, in the presence of a subthreshold concentration (1 nmol/L) of the beta-adrenergic agonist isoproterenol (Iso), genistein caused a near-maximal activation of this current. In the absence of genistein, Iso activated I-Cl with an EC50 of 5 nmol/L. In the presence of genistein, Iso activated I-Cl with an EC50 of 0.3 nmol/L. This facilitatory effect was not observed in the presence of daidzein (50 mu mol/L), an analogue of genistein that only weakly inhibits tyrosine kinase activity. Furthermore, peroxovanadate, a potent inhibitor of phosphotyrosine phosphatase activity, inhibited I-Cl activated by Iso alone, and it blocked the stimulatory effect of genistein in the presence of Iso. To determine whether the stimulatory effect of genistein was specific for I-Cl, we also studied its action on the cAMP-regulated delayed rectifier K+ current (I-K) and L-type Ca2+ current (ICa-L) present in these cells. Basal I-K and ICa-L were partially (approximate to 30% to 40%) inhibited by genistein. However, this inhibitory effect was mimicked by daidzein, suggesting that inhibition of tyrosine kinase activity is not involved. In addition to the nonspecific inhibitory effect, genistein also caused a significant increase in the beta-adrenergic sensitivity of the unblocked cationic currents. In the absence of genistein, 1 nmol/L Iso had no effect on either I-K or ICa-L. However, in the presence of genistein, 1 nmol/L Iso significantly increased the magnitude of both currents. These results suggest that tyrosine kinase activity may play an important role in regulating beta-adrenergic responsiveness of the heart.