Kück-Biere U, von Engelhardt W
Department of Physiology, School of Veterinary Medicine, Hannover, Federal Republic of Germany.
Gut. 1990 Jan;31(1):64-9. doi: 10.1136/gut.31.1.64.
K+ concentrations were measured in vitro with K+ sensitive microelectrodes in the microclimate at the luminal cell surface of the colon of guinea pigs. The serosal K+ concentration was mostly 5.4 mmol/1, the mucosal K+ concentrations were changed (0, 5, 50, or 70 mmol/l). Under control conditions K+ concentrations in the microclimate of the proximal colon were also low (6-9 mmol/l) and rather independent from K+ concentrations in the bulk luminal solution. In the distal colon K+ concentrations in the microclimate increased from 3.7 mmol/l when no K+ was in the luminal solution, up to 22 mmol/l when the mucosal K+ concentrations was 70 mmol/l. Attempts to decrease K+ conductance of the apical membrane with Ba++, to impair K+ transport with ouabain and to increase the paracellular shunt with deoxycholic acid did not affect K+ concentrations in the microclimate of the proximal colon but decreased K+ concentrations in the distal colon. When valinomycin or triaminopyrimidine were added to the mucosal solution at high K+ concentrations in the luminal solutions the K+ concentration in the microclimate was raised. At low luminal K+ concentrations valinomycin had no effect, triaminopyrimidine significantly diminished K+ concentrations at the cell surface. Regional differences in paracellular shunt conductance and in the preepithelial diffusion barrier are thought to be responsible for the observed differences between the proximal and the distal colon. Obviously, however, further unknown mechanisms have to be involved.
用钾离子敏感微电极在豚鼠结肠腔面细胞表面的微环境中进行体外钾离子浓度测量。浆膜侧钾离子浓度大多为5.4 mmol/L，黏膜侧钾离子浓度有所变化（0、5、50或70 mmol/L）。在对照条件下，近端结肠微环境中的钾离子浓度也较低（6 - 9 mmol/L），且与管腔大量溶液中的钾离子浓度相当独立。在远端结肠，当管腔溶液中无钾离子时，微环境中的钾离子浓度从3.7 mmol/L开始升高，当黏膜侧钾离子浓度为70 mmol/L时，升高至22 mmol/L。用钡离子降低顶端膜的钾离子电导、用哇巴因损害钾离子转运以及用脱氧胆酸增加细胞旁分流，均未影响近端结肠微环境中的钾离子浓度，但降低了远端结肠中的钾离子浓度。当在管腔溶液中高钾离子浓度时向黏膜溶液中添加缬氨霉素或三氨基嘧啶，微环境中的钾离子浓度会升高。在管腔低钾离子浓度时，缬氨霉素无作用，三氨基嘧啶显著降低细胞表面的钾离子浓度。细胞旁分流电导和上皮前扩散屏障的区域差异被认为是近端结肠和远端结肠之间观察到差异的原因。然而，显然还涉及进一步的未知机制。
