Naftalin R J, Tripathi S
J Physiol. 1985 Mar;360:27-50. doi: 10.1113/jphysiol.1985.sp015602.
Water flows generated by osmotic and hydrostatic pressure and electrical currents were measured in sheets of isolated rabbit ileum at 20 degrees C. Flows across the mucosal and serosal surfaces were monitored continuously by simultaneous measurement of tissue volume change (with an optical lever) and net water flows across one surface of the tissue (with a capacitance transducer). Osmotic gradients were imposed across the mucosal and serosal surfaces of the tissue separately, using probe molecules of various sizes from ethanediol (68 Da) to dextrans (161 000 Da). Flows across each surface were elicited with very short delay. The magnitudes of the flows were proportional to the osmotic gradient and related to the size of the probe molecule. Osmotic flow across the mucosal surface was associated with streaming potentials which were due to electro-osmotic water flow. The mucosal surface is a heteroporous barrier with narrow (0.7 nm radius, Lp (hydraulic conductivity) = (7.6 +/- 1.6) X 10(-9) cm s-1 cmH2O-1) cation-selective channels in parallel with wide neutral pores (ca. 6.5 nm radius, Lp = (2.3 +/- 0.2) X 10(-7) cm s-1 cmH2O-1) which admit large pressure-driven backflows from the submucosa to the lumen. There is additional evidence for a further set of narrow electroneutral pores less than 0.4 nm radius with Lp less than 7 X 10(-9) cm s-1 cmH2O-1. The serosal surface has neutral pores of uniform radius (ca. 6.5 nm), Lp = (7.6 +/- 1.6) X 10(-8) cm s-1 cmH2O-1. Hypertonic serosal solutions (100 mM-sucrose) cause osmotic transfer of fluid from isotonic mucosal solutions into the submucosa, expand it, and elevate the tissue pressure to 19.6 +/- 3.2 cmH2O (n = 4). Conversely, hypertonic mucosal solutions (100 mM-sucrose) draw fluid out of the submucosa in the presence of isotonic serosal solutions, collapse the submucosa, and lower the tissue pressure to -87.7 +/- 4.6 cmH2O (n = 5). Water flows coupled to cation movement could be generated across the mucosal surface in both directions by brief direct current pulses. The short latency of onset and cessation of flow (less than 2 s), absence of polarization potentials, and high electro-osmotic coefficients (range 50-520 mol water F-1), together with the presence of streaming potentials during osmotically generated water flows indicate electro-osmotic water flow through hydrated channels in the tight junctions and/or lateral intercellular spaces.(ABSTRACT TRUNCATED AT 400 WORDS)
在20摄氏度下，对分离出的兔回肠片的渗透、静水压和电流所产生的水流进行了测量。通过同时测量组织体积变化（用光学杠杆）和穿过组织一个表面的净水流（用电容传感器），持续监测穿过黏膜和浆膜表面的水流。分别在组织的黏膜和浆膜表面施加渗透梯度，使用从乙二醇（68道尔顿）到葡聚糖（161000道尔顿）等各种大小的探针分子。穿过每个表面的水流产生延迟非常短。水流的大小与渗透梯度成正比，并且与探针分子的大小有关。穿过黏膜表面的渗透流与由于电渗水流引起的流动电位有关。黏膜表面是一种异质多孔屏障，有狭窄的（半径0.7纳米，水力传导率Lp = (7.6 ± 1.6)×10⁻⁹厘米·秒⁻¹·厘米水柱⁻¹）阳离子选择性通道，与宽的中性孔（约6.5纳米半径，Lp = (2.3 ± 0.2)×10⁻⁷厘米·秒⁻¹·厘米水柱⁻¹）并行，这些宽孔允许从黏膜下层到管腔的大量压力驱动的回流。还有证据表明存在另一组半径小于0.4纳米、Lp小于7×10⁻⁹厘米·秒⁻¹·厘米水柱⁻¹的狭窄电中性孔。浆膜表面有半径均匀（约6.5纳米）的中性孔，Lp = (7.6 ± 1.6)×10⁻⁸厘米·秒⁻¹·厘米水柱⁻¹。高渗的浆膜溶液（100毫摩尔蔗糖）导致液体从等渗的黏膜溶液渗透转移到黏膜下层，使其扩张，并将组织压力升高到19.6 ± 3.2厘米水柱（n = 4）。相反，在等渗浆膜溶液存在的情况下，高渗的黏膜溶液（100毫摩尔蔗糖）将液体从黏膜下层吸出，使黏膜下层塌陷，并将组织压力降低到 - 87.7 ± 4.6厘米水柱（n = 5）。通过短暂的直流脉冲，可以在黏膜表面双向产生与阳离子移动相关的水流。水流开始和停止的延迟很短（小于2秒），不存在极化电位，并且电渗系数很高（范围为50 - 520摩尔水·法拉⁻¹），以及在渗透产生的水流过程中存在流动电位，这些都表明电渗水流通过紧密连接和/或细胞间侧向间隙中的水合通道。（摘要截断于400字）
