An ATP-gated cation channel with some P2Z-like characteristics in gastric smooth muscle cells of toad.
An ATP-gated cation channel with some P2Z-like characteristics in gastric smooth muscle cells of toad.
复制标题
蟾蜍胃平滑肌细胞中具有一些 P2Z 样特征的 ATP 门控阳离子通道。
DOI：
10.1113/jphysiol.1997.sp021869
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
WalshJr,JV
中科院分区：
文献类型：
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作者：
Ugur,M;Drummond,RM;Zou,H;Sheng,P;Singer,JJ;WalshJr,JV
1. 使用标准膜片钳和微荧光技术，研究了蟾蜍 Bufo marinus 胃中新鲜分离的平滑肌细胞中由细胞外 ATP 引起的全细胞和单通道电流。 2. 这种 ATP 门控阳离子通道与天然大鼠子宫肌层受体、某些天然 P2Z 嘌呤受体和最近克隆的 P2X7 嘌呤受体具有许多药理学和功能特性。但是，与后两者不同的是，ATP 门控通道不会介导大的非特异性孔的形成。因此，它可能代表 P2X 或 P2Z 类的新成员。 3. 细胞外应用 ATP（> 或 = 150 µM）会在负保持电位下引发内向全细胞电流，该电流是内向整流的，并且没有显示出脱敏迹象。 Na+、Cs+ 以及较小程度的有机阳离子胆碱充当电荷载体，但 Cl- 则不然。比率 Fura-2 测量表明电流部分由 Ca2+ 承载。在低二价阳离子浓度的溶液中，ATP 的 EC50 为 700 µM。 4. 细胞附着或切除斑块的细胞外表面的 ATP（> 或 = 100 microM）会引发电导为 22 pS 的内向整流单通道电流。 Cl- 不充当电荷载体，但 Na+ 和 Cs+ 都充当电荷载体，胆碱也起到较小程度的作用。通道的平均开放时间相当长，在保持电势为 ‐70 mV 时范围为数百毫秒。 5. Mg2+和Ca2+降低了ATP诱导的全细胞电流的强度。 Mg2+ 降低了 ATP 激活的单通道电流的幅度和活性。 6. ADP、UTP、P1、P5-二腺苷五磷酸 (AP5A)、腺苷和 α, β-亚甲基 ATP (α, β-Me-ATP) 不会诱导显着的全细胞电流。 ATP-gamma-S 和 2-甲硫基 ATP (2-Me-S-ATP) 在诱导全细胞电流方面明显不如 ATP 有效，而苯甲酰苯甲酰 ATP (BzATP) 则更有效。 BzATP、α、β-Me-ATP、ATP-gamma-S 和 2-Me-S-ATP 诱导单通道电流，但需要更高浓度的 α、β-Me-ATP。 7. 使用 mag-fura-2 作为高分子质量探针进行测定，BzATP 不会诱导大的非特异性孔的形成。
1. Whole‐cell and single‐channel currents elicited by extracellular ATP were studied in freshly dissociated smooth muscle cells from the stomach of the toad Bufo marinus using standard patch clamp and microfluorimetric techniques. 2. This ATP‐gated cation channel shares a number of pharmacological and functional properties with native rat myometrium receptors, certain native P2Z purinoceptors and the recently cloned P2X7 purinoceptor. But, unlike the last two, the ATP‐gated channel does not mediate the formation of large non‐specific pores. Thus, it may represent a novel member of the P2X or P2Z class. 3. Extracellular application of ATP (> or = 150 microM) elicited an inward whole‐cell current at negative holding potentials that was inwardly rectifying and showed no sign of desensitization. Na+, Cs+ and, to a lesser degree, the organic cation choline served as charge carriers, but Cl‐ did not. Ratiometric fura‐2 measurements indicated that the current is carried in part by Ca2+. The EC50 for ATP was 700 microM in solutions with a low divalent cation concentration. 4. ATP (> or = 100 microM) at the extracellular surface of cell‐attached or excised patches elicited inwardly rectifying single‐channel currents with a 22 pS conductance. Cl‐ did not serve as a charge carrier but both Na+ and Cs+ did, as did choline to a lesser extent. The mean open time of the channel was quite long, with a range in hundreds of milliseconds at a holding potential of ‐70 mV. 5. Mg2+ and Ca2+ decreased the magnitude of the ATP‐induced whole‐cell currents. Mg2+ decreased both the amplitude and the activity of ATP‐activated single‐channel currents. 6. ADP, UTP, P1, P5‐di‐adenosine pentaphosphate (AP5A), adenosine and alpha, beta‐methylene ATP (alpha, beta‐Me‐ATP) did not induce significant whole‐cell current. ATP‐gamma‐S and 2‐methylthio ATP (2‐Me‐S‐ATP) were significantly less effective than ATP in inducing whole‐cell currents, whereas benzoylbenzoyl ATP (BzATP) was more effective. BzATP, alpha, beta‐Me‐ATP, ATP‐gamma‐S and 2‐Me‐S‐ATP induced single‐channel currents, but a higher concentration of alpha, beta‐Me‐ATP was required. 7. BzATP did not induce the formation of large non‐specific pores, as assayed using mag‐fura‐2 as a high molecular mass probe.