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Blocking effects of extracellular Ba2+ on the inward rectifier potassium channel
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- Author:
- No author available
- Journal Title:
- ACTA PHYSIOLOGICA SINICA
- Issue:
- 1
- DOI:
- No doi available
- Key Word:
- Ba2+;内向整流钾通道;电压箝;爪蟾卵母细胞
Abstract： 实验采用双微电极电压箝(TEV)法研究Ba2+对非洲爪蟾卵母细胞表达的内向整流钾通道(IRK1)的阻断作用. 细胞外Ba2+浓度分别为0,1,3,10和100 μmol/L,K+浓度分别为10和90 mmol/L,可见快速开通道阻断剂Ba2+对IRK1的瞬间电流(施加电压后1 ms)的阻断作用依赖Ba2+、K+、时间和电压;但对IRK1的开关特性几乎无影响,IRK1对之不通透.三级指数拟合的结果表明: 细胞外Ba2+低浓度(1和3 μmol/L)时,Ba2+与K+相互竞争同一结合位点,随着Ba2+浓度的增加,时间常数不增加但拟合的权数却呈浓度依赖性增加,所以失活过程随Ba2+浓度的增加越来越快;细胞外Ba2+高浓度(10和100 μmol/L)时,时间常数随Ba2+浓度的增加而减少,拟合的权数却呈浓度依赖性减少,失活过程也越来越快,说明Ba2+作用位点由通道的表面进入了通道更深的部位. 上述结果提示,Ba2+对IRK1的阻断存在两种不同的机制.细胞外K+浓度为90 mmol/L和Ba2+浓度为30 μmol/L时,Mg2+或Mn2+可与Ba2+争夺结合位点,随着Mg2+或Mn2+浓度增加,失活过程逐渐减缓,Ba2+在通道中的结合点也逐渐离开通道,Mg2+能而Mn2+不能进入通道较深处阻断通道,说明IRK1中有多离子阻断形式.
- [1]D A, Doyle,J, Morais Cabral,R A, Pfuetzner,etc.The structure of the potassium channel: molecular basis of K+ conduction and selectivity.[J].1998,280.
- [2]S. Oiki,T. Yamamoto,Y. Okada.Apparent stability constants and purity of Ca-chelating agents evaluated using Ca-selective electrodes by the double-log optimization method[J].1994,15(3).
- [3]Sabirov, Ravshan Z.,Tominaga, Tomoko.A conserved arginine residue in the pore region of an inward rectifier K channel (IRK1) as an...[J].1997,110(6).
- [4]Collins A.,Chuang H.-h.,Jan Y. N.,etc.Scanning mutagenesis of the putative transmembrane segments of Kir2.1, an inward rectifier potassium channel[J].1997.
- [5]Y, Kubo,T J, Baldwin,Y N, Jan,etc.Primary structure and functional expression of a mouse inward rectifier potassium channel.[J].1993,362(6416).
- [6]R, MacKinnon,R, Latorre,C, Miller.Role of surface electrostatics in the operation of a high-conductance Ca2+-activated K+ channel.[J].1989,28.
- [7]B M, Block,W C, Stacey,S W, Jones.Surface charge and lanthanum block of calcium current in bullfrog sympathetic neurons.[J].1998,74(5).