Köckerling A, Sorgenfrei D, Fromm M
Institut für Klinische Physiologie, Klinikum Steglitz, Freie Universität Berlin, Germany.
Am J Physiol. 1993 May;264(5 Pt 1):C1285-93. doi: 10.1152/ajpcell.1993.264.5.C1285.
There is no quantitative assignment of large intestinal electrogenic Na+ absorption to surface epithelium and crypts so far. We determined the spatial distribution of electrogenic Na+ absorption to crypts and surface epithelium of rat late distal colon using a modified voltage-scanning technique. Voltage deflections resulting from external 30-Hz current were sensed by an extracellular microelectrode stepping at 0.7 Hz above crypt openings or surface epithelium. Local conductances were calculated applying a planar model of electrical field distribution to surface epithelium and a electrostatic disk source model to the crypts. These models were confirmed by methodological experiments where the electrode position was varied in vertical and horizontal direction. Electrogenic Na+ absorption was detected by blocking apical Na+ channels by mucosal 0.1 mM amiloride. Under control conditions surface epithelium contributed 44% (2.0 +/- 0.2 mS/cm2) and crypts 56% (2.6 +/- 0.2 mS/cm2) to the total conductance of 4.6 +/- 0.4 mS/cm2. Electrogenic Na+ absorption was induced by 6 h in vitro incubation in a medium containing 3 nM aldosterone. This caused a short-circuit current (ISC) of 12.1 +/- 0.8 mumol.h-1.cm-2, which was paralleled by a 2.5-fold increase in surface epithelial conductance to 5.1 +/- 0.4 mS/cm2, whereas crypt conductance was not significantly altered (3.0 +/- 0.2 mS/cm2). Amiloride reversed ISC to -0.8 +/- 0.1 mumol.-1.cm-2 and decreased surface epithelium conductance to 2.3 +/- 0.3 mS/cm2 but again had no significant effect on crypt conductance (2.5 +/- 0.3 mS/cm2). Sham incubation (no hormones added) for 6 h neither induced electrogenic transport nor altered local epithelial conductances.(ABSTRACT TRUNCATED AT 250 WORDS)
迄今为止，尚未对大肠表面上皮和隐窝的电生性钠吸收进行定量分配。我们使用改良的电压扫描技术，确定了大鼠远端结肠晚期隐窝和表面上皮的电生性钠吸收的空间分布。由外部30Hz电流引起的电压偏转由一个细胞外微电极在隐窝开口或表面上皮上方以0.7Hz的步长进行检测。通过将电场分布的平面模型应用于表面上皮，并将静电盘源模型应用于隐窝来计算局部电导。这些模型通过方法学实验得到了证实，在这些实验中，电极位置在垂直和水平方向上发生变化。通过黏膜给予0.1mM氨氯地平阻断顶端钠通道来检测电生性钠吸收。在对照条件下，表面上皮对总电导4.6±0.4mS/cm²的贡献为44%（2.0±0.2mS/cm²），隐窝为56%（2.6±0.2mS/cm²）。通过在含有3nM醛固酮的培养基中体外孵育6小时诱导电生性钠吸收。这导致短路电流（ISC）为12.1±0.8μmol·h⁻¹·cm⁻²，同时表面上皮电导增加2.5倍，达到5.1±0.4mS/cm²，而隐窝电导没有显著改变（3.0±0.2mS/cm²）。氨氯地平将ISC逆转至-0.8±0.1μmol·h⁻¹·cm⁻²，并将表面上皮电导降低至2.3±0.3mS/cm²，但再次对隐窝电导没有显著影响（2.5±0.3mS/cm²）。假孵育（不添加激素）6小时既未诱导电生性转运，也未改变局部上皮电导。（摘要截断于250字）
