Wang Yong G, Dedkova Elena N, Steinberg Susan F, Blatter Lothar A, Lipsius Stephen L
Stritch School of Medicine, Department of Physiology, Loyola University Medical Center, 2160 South First Avenue, Maywood, IL 60153, USA.
J Gen Physiol. 2002 Jan;119(1):69-82. doi: 10.1085/jgp.119.1.69.
In atrial myocytes, an initial exposure to isoproterenol (ISO) acts via cAMP to mediate a subsequent acetylcholine (ACh)-induced activation of ATP-sensitive K(+) current (I(K,ATP)). In addition, beta-adrenergic receptor (beta-AR) stimulation activates nitric oxide (NO) release. The present study determined whether the conditioning effect of beta-AR stimulation acts via beta(1)- and/or beta(2)-ARs and whether it is mediated via NO signaling. 0.1 microM ISO plus ICI 118,551 (ISO-beta(1)-AR stimulation) or ISO plus atenolol (ISO-beta(2)-AR stimulation) both increased L-type Ca(2+) current (I(Ca,L)) markedly, but only ISO-beta(2)-AR stimulation mediated ACh-induced activation of I(K,ATP). 1 microM zinterol (beta(2)-AR agonist) also increased I(Ca,L) and mediated ACh-activated I(K,ATP). Inhibition of NO synthase (10 microM L-NIO), guanylate cyclase (10 microM ODQ), or cAMP-PKA (50 microM Rp-cAMPs) attenuated zinterol-induced stimulation of I(Ca,L) and abolished ACh-activated I(K,ATP). Spermine-NO (100 microM; an NO donor) mimicked beta(2)-AR stimulation, and its effects were abolished by Rp-cAMPs. Intracellular dialysis of 20 microM protein kinase inhibitory peptide (PKI) abolished zinterol-induced stimulation of I(Ca,L). Measurements of intracellular NO (NO) using the fluorescent indicator DAF-2 showed that ISO-beta(2)-AR stimulation or zinterol increased NO. L-NIO (10 microM) blocked ISO- and zinterol-induced increases in NO. ISO-beta(1)-AR stimulation failed to increase NO. Inhibition of G(i)-protein by pertussis toxin significantly inhibited zinterol-mediated increases in NO. Wortmannin (0.2 microM) or LY294002 (10 microM), inhibitors of phosphatidylinositol 3'-kinase (PI-3K), abolished the effects of zinterol to both mediate ACh-activated I(K,ATP) and stimulate NO. We conclude that both beta(1)- and beta(2)-ARs stimulate cAMP. beta(2)-ARs act via two signaling pathways to stimulate cAMP, one of which is mediated via G(i)-protein and PI-3K coupled to NO-cGMP signaling. Only beta(2)-ARs acting exclusively via NO signaling mediate ACh-induced activation of I(K,ATP). NO signaling also contributes to beta(2)-AR stimulation of I(Ca,L). The differential effects of beta(1)- and beta(2)-ARs can be explained by the coupling of these two beta-ARs to different effector signaling pathways.
在心房肌细胞中，首次暴露于异丙肾上腺素（ISO）可通过环磷酸腺苷（cAMP）介导随后乙酰胆碱（ACh）诱导的三磷酸腺苷敏感性钾电流（I(K,ATP)）激活。此外，β-肾上腺素能受体（β-AR）刺激可激活一氧化氮（NO）释放。本研究确定β-AR刺激的预处理效应是否通过β(1)-和/或β(2)-AR起作用，以及是否通过NO信号介导。0.1微摩尔/升ISO加ICI 118,551（ISO-β(1)-AR刺激）或ISO加阿替洛尔（ISO-β(2)-AR刺激）均显著增加L型钙电流（I(Ca,L)），但只有ISO-β(2)-AR刺激介导ACh诱导的I(K,ATP)激活。1微摩尔/升齐特罗尔（β(2)-AR激动剂）也增加I(Ca,L)并介导ACh激活的I(K,ATP)。抑制一氧化氮合酶（10微摩尔/升L-NIO）、鸟苷酸环化酶（10微摩尔/升ODQ）或cAMP-蛋白激酶A（50微摩尔/升Rp-cAMPs）可减弱齐特罗尔诱导的I(Ca,L)刺激，并消除ACh激活的I(K,ATP)。精胺-NO（100微摩尔/升；一种NO供体）模拟β(2)-AR刺激，其作用被Rp-cAMPs消除。用20微摩尔/升蛋白激酶抑制肽（PKI）进行细胞内透析可消除齐特罗尔诱导的I(Ca,L)刺激。使用荧光指示剂DAF-2测量细胞内NO（NO）表明，ISO-β(2)-AR刺激或齐特罗尔增加NO）。10微摩尔/升L-NIO阻断ISO和齐特罗尔诱导的NO增加。ISO-β(1)-AR刺激未能增加NO）。百日咳毒素抑制G(i)-蛋白可显著抑制齐特罗尔介导的NO增加。渥曼青霉素（0.2微摩尔/升）或LY294002（10微摩尔/升），磷脂酰肌醇3'-激酶（PI-3K）抑制剂，消除了齐特罗尔介导ACh激活I(K,ATP)和刺激NO的作用。我们得出结论，β(1)-和β(2)-AR均刺激cAMP。β(2)-AR通过两条信号通路刺激cAMP，其中一条通过与NO-cGMP信号偶联的G(i)-蛋白和PI-3K介导。只有仅通过NO信号起作用的β(2)-AR介导ACh诱导的I(K,ATP)激活。NO信号也有助于β(2)-AR对I(Ca,L)的刺激。β(1)-和β(2)-AR的不同作用可通过这两种β-AR与不同效应器信号通路的偶联来解释。
