Different properties of the atrial G protein-gated K+ channels activated by extracellular ATP and adenosine.
Different properties of the atrial G protein-gated K+ channels activated by extracellular ATP and adenosine.
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细胞外 ATP 和腺苷激活心房 G 蛋白门控 K 通道的不同特性。
DOI：
10.1152/ajpheart.1995.269.4.h1349
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Kim,D
中科院分区：
文献类型：
--
作者：
Fu,C;Pleumsamran,A;Oh,U;Kim,D
细胞外 ATP (ATPo) 和腺苷激活心房细胞中 G 蛋白门控的内向整流 K+ 电流。早期研究表明，这两种激动剂可能使用不同的途径来激活 K+ 电流。因此，我们检查了两种激动剂激活的 K+ 通道在相同离子条件下是否具有不同的特性。在细胞贴附斑块中，移液管中 100 µM ATP 激活的 K+ 通道的单通道电导和平均开放时间分别为 32.0 +/- 0.2 pS 和 0.5 +/- 0.1 ms，而腺苷 (140 mM KCl) 激活的 K+ 通道的单通道电导和平均开放时间分别为 31.3 +/- 0.3 pS 和 0.9 +/- 0.1 ms。以 ATPo 作为激动剂，细胞附着斑块中的 K+ 通道活性大约比浸浴中含有 100 µM GTP 的由内而外的斑块低三倍。将 ATP 应用于膜的细胞质侧 (ATPi) 对通道活性产生双相浓度依赖性效应：低浓度时增加[平均亲和常数 (K0.5) = 190 microM]，高浓度时减少 (K0.5 = 1.3 mM)。相比之下，使用腺苷作为激动剂时，细胞附着斑块中的 K+ 通道活性大约是浸浴中含有 100 µM GTP 的由内而外的斑块中的四倍。在由内而外的贴片中，ATPi 仅增强 K+ 通道活性 (K0.5 = 32 microM)。这些结果表明，尽管ATPo和腺苷在心房细胞中激活动力学相似的K+通道，但细胞内核苷酸对这些通道的调节不同。
Extracellular ATP (ATPo) and adenosine activate G protein-gated inwardly rectifying K+ currents in atrial cells. Earlier studies have suggested that the two agonists may use separate pathways to activate the K+ current. Therefore, we examined whether the K+ channels activated by the two agonists have different properties under identical ionic conditions. In cell-attached patches, K+ channels activated by 100 microM ATP in the pipette had a single-channel conductance and mean open time of 32.0 +/- 0.2 pS and 0.5 +/- 0.1 ms, respectively, compared with 31.3 +/- 0.3 pS and 0.9 +/- 0.1 ms for the K+ channels activated by adenosine (140 mM KCl). With ATPo as the agonist, the K+ channel activity in cell-attached patches was approximately threefold lower than that in inside-out patches with 100 microM GTP in the bath. Applying ATP to the cytoplasmic side of the membrane (ATPi) produced a biphasic concentration-dependent effect on channel activity: an increase at low [mean affinity constant (K0.5) = 190 microM] and a decrease at high (K0.5 = 1.3 mM) concentrations. In contrast, with adenosine as the agonist, K+ channel activity in cell-attached patches was approximately fourfold greater than that in inside-out patches with 100 microM GTP in the bath. In inside-out patches, ATPi only augmented the K+ channel activity (K0.5 = 32 microM). These results show that although both ATPo and adenosine activate kinetically similar K+ channels in atrial cells, the channels are regulated differently by intracellular nucleotides.