Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes.
Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes.
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哇巴因对犬结肠肌细胞背景和电压依赖性电流的影响。
DOI：
10.1152/ajpcell.1990.259.3.c402
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Sanders,KM
中科院分区：
文献类型：
--
作者：
Burke,EP;Sanders,KM
以往的研究表明，犬近端结肠环状肌层的膜电位梯度是由于Na(+)-K(+)-ATPase贡献的梯度所致。粘膜下缘的细胞产生大约35 mV的泵电位，而肌间缘的泵对静息电位的贡献很小。泵被阻断的完整肌肉实验结果有些难以解释，因为泵抑制剂可能会对膜电导产生影响。因此，我们对分离的结肠肌细胞进行了研究，以测试哇巴因对被动膜特性和电压依赖性电流的影响。哇巴因(10(-5)M)使细胞去极化，并使输入电阻从0.487+/-0.060降至0.292+/-0.040 G omega。电阻的降低归因于K+电导的增加。还进行了测量哇巴因依赖电流的研究。37℃时，在细胞内Na+浓度为19 mM的透析细胞中，哇巴因引起的内向电流平均为71.06+/-7.49 pA，这归因于阻断泵电流。在24℃或低[Na+]i(11 Mm)透析的细胞中，哇巴因对保持电流几乎没有影响。在结肠细胞的输入电阻作用下，泵电流似乎能够产生至少35 mV。因此，生电Na+泵可以显著提高膜电位。
Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.