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：1987
卷号：84
期号：8
页码：2560-2564
DOI：10.1073/pnas.84.8.2560
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The mechanism of rectification of the inwardly rectifying potassium channel was examined with single-channel recording techniques in isolated ventricular myocytes from adult guinea pig heart. Inward, or anomalous, rectification describes the property that potassium (K) current can enter the cell at potentials negative to the potassium equilibrium potential, EK, more readily than it can leave the cell at positive potentials. Voltage ramps applied to single inward rectifier channels in cell-attached patches produced single-channel currents that rectified strongly with a marked reduction in current at a potential near EK. At more positive potentials no current could be detected. Rectification was influenced by external and internal K concentrations. Single-channel activity, which usually disappears rapidly in excised patches, could be maintained by removing calcium from the internal solution. Rectification could be eliminated by excision of the patch into an internal solution in which free magnesium (Mg2+) was reduced to less than 1 microM, and it could be restored by the addition of approximately 1 mM Mg2+ to the internal solution. At intermediate concentrations of Mg2+, intermediate degrees of rectification were obtained, and the current at potentials positive to EK was often interrupted by brief closures. These studies suggest that rectification is due to internal block by Mg2+, possibly the result of rapid block of the open channel.
