Blocking agents of Ca2+-activated K+ channels in cultured medullary thick ascending limb cells.
Blocking agents of Ca2+-activated K+ channels in cultured medullary thick ascending limb cells.
复制标题
培养的髓质厚升肢细胞中 Ca2 激活 K 通道的阻断剂。
DOI：
10.1152/ajpcell.1987.252.2.c128
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Sacktor,B
中科院分区：
文献类型：
--
作者：
Guggino,SE;Guggino,WB;Green,N;Sacktor,B
在培养的髓质粗升支（MTAL）细胞克隆A3的顶端细胞膜中鉴定了钙激活的K+通道，估计单通道电导为127 +/- 2 pS。Ba 2+和蝎毒素Charybdotoxin（CTX）都是通道的缓慢阻断剂。将0.1 μ M的Ba 2+应用于细胞内表面导致开放时间分数（fv）减少50%。Ba ~（2+）阻滞具有浓度依赖性和电压依赖性。细胞外溶液中低至2 nM的CTX浓度导致Fv显著降低。四乙基铵（TEA）和奎宁是MTAL细胞中Ca 2+激活的K+通道的快速阻断剂。TEA，400 μ M，在细胞外溶液中引起通道振幅的电压依赖性降低，而在细胞内溶液中需要10 mM才能将通道振幅降低30%。微摩尔量的奎宁应用于细胞内的面引起的通道之间迅速闪烁开放和封锁状态。这些结果表明，在MTAL细胞中的K+通道是同源的肌肉细胞中发现的，这些阻断剂可用于探测K+电导在几个肾单位段的性质。
Ca2+-activated K+ channels with estimated single channel conductances of 127 +/- 2 pS were identified in the apical cell membrane of clone A3 of cultured medullary thick ascending limb (MTAL) cells. Both Ba2+ and the scorpion toxin, charybdotoxin (CTX), are slow blockers of the channels. An application of 0.1 microM Ba2+ to the intracellular face caused a 50% reduction in fractional open time (fv). Ba2+ block is both concentration and voltage dependent. Concentrations of CTX as low as 2 nM in the extracellular solution caused a significant reduction in fv. Tetraethylammonium (TEA) and quinine are fast blockers of Ca2+-activated K+ channels in MTAL cells. TEA, 400 microM, in the extracellular solution caused a voltage-dependent reduction in channel amplitude, whereas it takes 10 mM in the intracellular solution to reduce channel amplitude by 30%. Micromolar amounts of quinine applied to the intracellular face caused the channels to flicker rapidly between open and blocked states. These results suggest that K+ channels in MTAL cells are homologous to those found in muscle cells, and that these blocking agents may be used to probe the nature of K+ conductances in several nephron segments.