期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1997
卷号：94
期号：14
页码：7651-7654
DOI：10.1073/pnas.94.14.7651
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Streaming potentials across cloned epithelial Na+ channels (ENaC) incorporated into planar lipid bilayers were measured. We found that the establishment of an osmotic pressure gradient ({Delta}{pi}) across a channel-containing membrane mimicked the activation effects of a hydrostatic pressure differential ({Delta}P) on {beta}{gamma}-rENaC, although with a quantitative difference in the magnitude of the driving forces. Moreover, the imposition of a {Delta}{pi} negates channel activation by {Delta}P when the {Delta}{pi} was directed against {Delta}P. A streaming potential of 2.0 {+/-} 0.7 mV was measured across {beta}{gamma}-rat ENaC (rENaC)-containing bilayers at 100 mM symmetrical [Na+] in the presence of a 2 Osmol/kg sucrose gradient. Assuming single file movement of ions and water within the conduction pathway, we conclude that between two and three water molecules are translocated together with a single Na+ ion. A minimal effective pore diameter of 3 A that could accommodate two water molecules even in single file is in contrast with the 2-A diameter predicted from the selectivity properties of {beta}{gamma}-rENaC. The fact that activation of {beta}{gamma}-rENaC by {Delta}P can be reproduced by the imposition of {Delta}{pi} suggests that water movement through the channel is also an important determinant of channel activity.
关键词：sodium transport ; epithelia ; amiloride ; water permeability ; mechanosensitivity
