Isoproterenol modulates the calcium channels through two different mechanisms in smooth-muscle cells from rabbit portal vein.
Isoproterenol modulates the calcium channels through two different mechanisms in smooth-muscle cells from rabbit portal vein.
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异丙肾上腺素通过两种不同的机制调节兔门静脉平滑肌细胞中的钙通道。
DOI：
10.1007/bf00374847
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Fenoglio-Preiser,C
中科院分区：
文献类型：
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作者：
Xiong,Z;Sperelakis,N;Fenoglio-Preiser,C
我们实验室前期的数据表明，血管平滑肌细胞的慢Ca2+通道受到环核苷酸的调节。在本研究中，使用全细胞电压钳技术，研究了异丙肾上腺素 (ISO) 对来自兔门静脉的新鲜分离的单个平滑肌细胞中 L 型钙电流 (ICa(L)) 的影响。使用移液管中的高 Cs+ 溶液和浴中的生理盐溶液（含有 2.0 mM Ca2+），记录 (ICa(L))。在-80 mV的保持电位下，低浓度的ISO（⩽ 100 nM）增加了ICa，而较高浓度（1-100 μM）短暂地增加了ICa，但随后持续抑制了它。在 10 μM ISO 时，IC 最初增加了 44±9%，随后下降了 24±3%。用30 μM H-7 [1-(5-异喹啉基磺酰基)-2-甲基哌嗪二盐酸盐]预处理细胞导致第一阶段持续存在，第二抑制阶段消失。细胞内应用 1 mM GDP[βS]（鸟苷 5'-O-2-硫代二磷酸）可消除 ISO 作用的两个阶段。相比之下，细胞内应用 100 μM GTP 会导致 ISO 作用的初始刺激阶段显着增强；后期抑制期略有减弱。此外，活化的G蛋白α亚基（Gsα）模仿ISO的刺激作用。百日咳毒素对 ISO 作用的任何一个阶段都没有影响。这些结果表明 ISO 通过涉及百日咳毒素不敏感 G 蛋白的机制来调节 Ca2+ 通道。 H-7 是一种非特异性蛋白激酶抑制剂，它能阻断第二阶段，但不能阻断第一阶段，这表明 ISO 的作用是通过两种不同的途径介导的。一种途径（用于抑制）更为间接，可能由腺苷酸环化酶/cAMP/蛋白激酶-A 级联介导。另一条途径（用于刺激）更直接，可能反映 Ca2+ 通道的一种 G 蛋白门控。
Previous data from our laboratory indicated that the slow Ca2+channel of vascular smooth muscle cells was regulated by cyclic nucleotides. In the present study, the effects of isoproterenol (ISO) on L-type calcium current (ICa(L)) were investigated in freshly-isolated single smooth-muscle cells from the rabbit portal vein using the whole-cell voltage-clamp technique. With high-Cs+solution in the pipette and physiolocial salt solution (containing 2.0 mM Ca2+) in the bath, (ICa(L)) was recorded. At a holding potential of −80 mV, low concentrations of ISO (⩽ 100 nM)increased ICa, whereas higher concentrations (1–100 μM) transiently increasedICabut then inhibited it persistently. At 10 μM ISO,ICawas initially increased by 44±9%, and was subsequently decreased by 24±3%. Pretreatment of cells with 30 μM H-7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine dihydrochloride] caused the first phase to persist and the second inhibitory phase to disappear. Intracellular application of 1 mM GDP[βS] (guanosine 5′-O-2-thiodiphosphate) abolished both phases of ISO action. In contrast, intracellular application of 100 μM GTP caused the initial stimulatory phase of ISO action to be significantly potentiated; the later inhibitory phase was slightly diminished. In addition, the activated G proteinαsubunit (Gsα) mimicked the stimulatory effect of ISO. Pertussis toxin had no effect on either phase of the ISO action. These results suggest that ISO modulates the Ca2+channel through mechanisms that involve the pertussis-toxin-insensitive G protein(s). That H-7, a nonspecific inhibitor of protein kinases, blocked the second phase but not the first phase indicates that the actions of ISO are mediated via two different pathways. One pathway (for inhibition) is more indirect, and may be mediated by the adenylate cyclase/cAMP/protein-kinase-A cascade. The other pathway (for stimulation) is more direct, and may reflect a type of G protein gating of the Ca2+channel.