Regulation of apical K and Na channels and Na/K pumps in rat cortical collecting tubule by dietary K.
Regulation of apical K and Na channels and Na/K pumps in rat cortical collecting tubule by dietary K.
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DOI：
10.1085/jgp.104.4.693
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发表时间：
1994-10
期刊：
影响因子：
--
通讯作者：
Frindt G
中科院分区：
文献类型：
--
作者：
Palmer LG;Antonian L;Frindt G
用膜片钳技术研究了大鼠皮质集合管顶膜上钾、钠通道的性质和密度。在细胞附着性斑块(SK通道)中观察到的主要K通道具有10ps的向外单通道电导(与移液管中的LiCl)。内向电导(在移液管中有KCl)为42ps。该通道具有很高的开放概率，并且随着去极化的增加而增加。动力学分析表明，存在单个开放状态和两个闭合状态。通过保持动物高钾饮食12-16天来增加钾摄入量，每片SK通道的数量比对照水平增加了三倍(0.7-2.0个/片)。此外，在低密度(0.5个/斑片)下观察到对照动物没有观察到的传导钠选择通道。这些通道具有与低钠饮食时观察到的相似的特性，只是平均开放概率(0.84)更高。在其他实验中，使用全细胞膜片钳技术测量钠通道活动(如阿米洛利敏感电流，INA)和钠泵活动(如哇巴因敏感电流，I泵)。在高钾饮食的动物中，INA高于对照组，但远低于低钠饮食的大鼠。钾负荷后I泵大于对照组或钠耗竭动物。这些K饮食依赖的效应并没有伴随着血浆醛固酮浓度的显著增加。为进一步探讨钾通道活性与糖皮质激素的关系，大鼠维持低钠饮食以增加内源性醛固酮的分泌。在此条件下，未观察到SK通道密度的增加，尽管Na通道的数量有较大的增加(至2.7个/Patch)。醛固酮也是通过渗透性微泵外源性给药。与低钠饮食一样，尽管Na通道被激活，但传导SK通道的密度没有改变。这些结果表明，在钾摄入量变化过程中，SK通道、Na通道和Na/K泵受醛固酮以外的其他因素的调节。
The patch-clamp technique was used to study the properties and the density of conducting K and Na channels in the apical membrane of rat cortical collecting tubule. The predominant K channel observed in cell- attached patches (SK channels) had an outward single-channel conductance (with LiCl in the pipette) of 10 pS. The inward conductance (with KCl in the pipette) was 42 pS. The channel had a high open probability that increased with depolarization. Kinetic analysis indicated the presence of a single open state and two closed states. Increasing K intake by maintaining animals on a high K diet for 12-16 d increased the number of SK channels per patch by threefold (0.7- 2.0/patch) over control levels. In addition, conducting Na-selective channels, which were not observed in control animals, were seen at low density (0.5/patch). These channels had properties similar to those observed when the animals were on a low Na diet, except that the mean open probability (0.84) was higher. In other experiments, the whole- cell patch clamp technique was used to measure Na channel activity (as amiloride-sensitive current, INa) and Na pump activity (as ouabain- sensitive current, Ipump). In animals on a high K diet, INa was greater than in controls but much less than in rats on a low Na diet. Ipump was greater after K loading than in controls or Na-depleted animals. These K diet-dependent effects were not accompanied by a significant increase in plasma aldosterone concentrations. To further investigate the relationship between K channel activity and mineralocorticoids, rats were maintained on a low Na diet to increase endogenous aldosterone secretion. Under these conditions, no increase in SK channel density was observed, although there was a large increase in the number of Na channels (to 2.7/patch). Aldosterone was also administered exogenously through osmotic minipumps. As with the low Na diet, there was no change in the density of conducting SK channels, although Na channel activity was induced. These results suggest that SK channels, Na channels and Na/K pumps are regulated during changes in K intake by factors other than aldosterone.