Membrane cholesterol extraction decreases Na+ transport in A6 renal epithelia
Membrane cholesterol extraction decreases Na+ transport in A6 renal epithelia
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DOI：
10.1152/ajpcell.00184.2005
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发表时间：
2006-01-01
影响因子：
5.5
通讯作者：
Jans, D
中科院分区：
文献类型：
--
作者：
Balut, C;Steels, P;Jans, D
在本研究中，我们研究了A6肾上皮细胞膜胆固醇含量对Na+转运调节的依赖性。我们连续监测短路电流（I-SC）、跨上皮电导（G（T））和跨上皮电容（CT），以评估在稳态条件下以及在低渗休克、催产素和腺苷激活期间从顶膜和基底侧膜提取胆固醇的效果。通过用甲基-β-环糊精（m β CD）灌注上皮细胞1小时来实现胆固醇提取。在稳态条件下，顶膜胆固醇提取没有显着影响电生理参数，相反，在基底外侧m β CD治疗期间观察到显着降低。然而，心尖m β CD应用阻碍了I-SC和G（T）对低渗、催产素和腺苷的反应。阻断剂诱导的I-SC波动的分析表明，顶端m β CD处理降低了稳态下以及腺苷激活Na+转运后的上皮Na+通道（ENaC）开放概率（P-O），而传导通道的密度没有显著变化，如CT测量所证实的。由于Na+/K+泵活性降低，在基底外侧m β CD治疗期间，低渗性导致的Na+转运激活被取消。在这项研究中的结果的基础上，我们得出结论，基底外侧膜胆固醇提取降低Na+/K+泵活性，而减少胆固醇含量的顶膜影响Na+转运的激活，减少ENaC P-O。
In this study, we have investigaed the dependence of Na+ transport regulation on membrane cholesterol content in A6 renal epithelia. We continuously monitored short-circuit current (I-SC), transepithelial conductance (G(T)), and transepithelial capacitance (CT) to evaluate the effects of cholesterol extraction from the apical and basolateral membranes in steady-state conditions and during activation with hyposmotic shock, oxytocin, and adenosine. Cholesterol extraction was achieved by perfusing the epithelia with methyl-beta-cyclodextrin (m beta CD) for 1 h. In steady-state conditions, apical membrane cholesterol extraction did not significantly affect the electrophysiological parameters; in contrast, marked reductions were observed during basolateral m beta CD treatment. However, apical m beta CD application hampered the responses of I-SC and G(T) to hypotonicity, oxytocin, and adenosine. Analysis of the blocker-induced fluctuation in I-SC demonstrated that apical m beta CD treatment decreased the epithelial Na+ channel (ENaC) open probability (P-O) in the steady state as well as after activation of Na+ transport by adenosine, whereas the density of conducting channels was not significantly changed as confirmed by CT measurements. Na+ transport activation by hypotonicity was abolished during basolateral m beta CD treatment as a result of reduced Na+/K+ pump activity. On the basis of the findings in this study, we conclude that basolateral membrane cholesterol extraction reduces Na+/K+ pump activity, whereas the reduced cholesterol content of the apical membranes affects the activation of Na+ transport by reducing ENaC P-O.