Role of the sodium pump and the background K+ channel in passive K+(Rb+) uptake by isolated cardiac sarcolemmal vesicles.
Role of the sodium pump and the background K+ channel in passive K+(Rb+) uptake by isolated cardiac sarcolemmal vesicles.
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钠泵和背景 K 通道在离体心脏肌膜囊泡被动 K (Rb) 摄取中的作用。
DOI：
10.1007/bf01872327
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Szabo,G
中科院分区：
文献类型：
--
作者：
Otero,AS;Szabo,G
开发了一种简单的程序，用于从牛蛙（Rana catesbeiana）心脏匀浆中分离富含肌膜的膜制剂。通过差速离心获得的粗微粒体在泛影葡胺密度梯度中分级。富含表面膜标记物的部分由 87% 紧密密封的囊泡组成。使用快速离子交换技术在相反的K + 梯度存在下测量制剂对86 Rb + 的吸收。在低泡外 Rb+ 浓度下，通过向测定培养基中添加 1mmouabain 可以阻断至少 50% 的吸收。在这些条件下，原钒酸盐 (50 μm)、ADP (2.5mm) 或 Mg (1mm) 也是 Rb+ 摄取的部分抑制剂，并在 1mmouabain 存在的情况下完全阻断 Rb+ 流入。当86Rb+用作囊外K+(Rb0+≤40μmK0+=0.1-5mm)的示踪剂时，出现了明显的摄取途径，如通过1mmBa2+(K0.5=20μm)的抑制所检测到的。在恒定的内部 K+ 浓度（Kin+=50mm）下，Ba2+ 敏感的 K+ 摄取的大小被发现以与在完整心肌细胞中电生理学观察到的背景 K+ 电导（IK1）的 K+ 浓度依赖性非常相似的方式依赖于 K0+。我们得出的结论是，K + 通过两个不同的途径（钠泵和可识别为背景钾通道的系统）被动地渗透到该制剂中。
A simple procedure was developed for the isolation of a sarcolemma-enriched membrane preparation from homogenates of bullfrog (Rana catesbeiana) heart. Crude microsomes obtained by differential centrifugation were fractionated in Hypaque density gradients. The fraction enriched in surface membrane markers consisted of 87% tightly sealed vesicles. The uptake of86Rb+by the preparation was measured in the presence of an opposing K+gradient using a rapid ion exchange technique. At low extravesicular Rb+concentrations, at least 50% of the uptake was blocked by addition of 1mmouabain to the assay medium. Orthovanadate (50 μm), ADP (2.5mm), or Mg (1mm) were also partial inhibitors of Rb+uptake under these conditions, and produced a complete block of Rb+influx in the presence of 1mmouabain. When86Rb+was used as a tracer of extravesicular K+(Rb0+≦40 μmK0+=0.1–5mm) a distinct uptake pathway emerged, as detected by its inhibition by 1mmBa2+(K0.5=20 μm). At a constant internal K+concentration (Kin+=50mm) the magnitude of the Ba2+-sensitive K+uptake was found to depend on K0+in a manner that closely resembles the K+concentration dependence of the background K+conductance (IKl) observed electrophysiologically in intact cardiac cells. We conclude that K+permeates passively this preparation through two distinct pathways, the sodium pump and a system identifiable as the background potassium channel.