Naftalin R J, Tripathi S
J Physiol. 1986 Jan;370:409-32. doi: 10.1113/jphysiol.1986.sp015942.
Water movements have been studied in sheets of isolated rabbit ileum using a method which measures net volume flows across the mucosal and serosal surfaces of the tissue continuously with high resolution. At 35 degrees C, with the tissues incubated in isotonic Ringer solution containing D-glucose (25 mM) on both sides, there is a steady net inflow of fluid at the rate of 24 +/- 2 microliter cm-2 h-1 across the mucosal surface (Jm) and an outflow of 8 +/- 1 microliter cm-2 h-1 across the serosal surface (Js) (n = 16). The stable transepithelial p.d. across these tissues is 2.7 +/- 0.2 mV, serosa positive. Jm can be reversibly inhibited by anoxia. Ouabain (0.1 mM) added to the serosal solution inhibits inflow across the mucosal and serosal surfaces by 75% (n = 7) within 30 min. If phlorizin (0.1 mM) is added to the mucosal Ringer solution containing glucose (20 mM) within 30 min of the commencement of in vitro absorption, Jm is reduced from 37 +/- 3 to 28 +/- 2 microliter cm-2 h-1 (n = 3). Dilution of the mucosal Ringer solution by 50 mosmol kg-1 (with the serosal solution kept isosmolar) results in a rapid transient increase in mucosal inflow. An increase of 50 mosmol kg-1 in the mucosal Ringer solution with NaCl, sucrose or mannitol causes a transient reversal of mucosal flow, followed by a return of inflow at a reduced level. Rabbit ileum can transport water against gradients of approximately 75 mosmol kg-1 of sucrose, NaCl, or mannitol. Addition of polyethylene glycol (mol. wt. 20000; 3 mosmol kg-1) causes a sustained reversal of mucosal inflow; inflow can be restored only by removing polyethylene glycol from the mucosal Ringer solution. The tissue can absorb water against an osmotic gradient of 200 mM-glycerol. The above data have been incorporated into a new model to explain isotonic flow of fluid by this epithelium. The main features are that the hydraulic conductivity (Lp) of the mucosal boundary of the lateral intercellular space is approximately 1 X 10(-8) cm s-1 cmH2O-1. This Lp is too low to sustain isotonicity of the flow emerging from the lateral intercellular space at the observed rates. Hypertonic fluid emerging from the lateral intercellular space is diluted by transcellular water flow generated by the hypertonicity of the submucosa and back-diffusion of solute via mucosal shunt channels.(ABSTRACT TRUNCATED AT 400 WORDS)
采用一种能以高分辨率连续测量跨组织黏膜和浆膜表面净体积流量的方法，对离体兔回肠片的水分运动进行了研究。在35摄氏度时，将组织置于两侧均含有D - 葡萄糖（25 mM）的等渗林格溶液中孵育，有稳定的净液体流入，速率为24±2微升·厘米⁻²·小时⁻¹，通过黏膜表面（Jm），而通过浆膜表面（Js）有8±1微升·厘米⁻²·小时⁻¹的流出（n = 16）。这些组织上稳定的跨上皮电位差为2.7±0.2毫伏，浆膜为正。Jm可被缺氧可逆性抑制。加入到浆膜溶液中的哇巴因（0.1 mM）在30分钟内使通过黏膜和浆膜表面的流入减少75%（n = 7）。如果在体外吸收开始30分钟内将根皮苷（0.1 mM）加入到含葡萄糖（20 mM）的黏膜林格溶液中，Jm从37±3降至28±2微升·厘米⁻²·小时⁻¹（n = 3）。将黏膜林格溶液稀释50毫渗摩尔·千克⁻¹（浆膜溶液保持等渗）会导致黏膜流入迅速短暂增加。用氯化钠、蔗糖或甘露醇使黏膜林格溶液增加50毫渗摩尔·千克⁻¹会导致黏膜流动短暂逆转，随后流入以降低的水平恢复。兔回肠能逆着约75毫渗摩尔·千克⁻¹的蔗糖、氯化钠或甘露醇梯度转运水。加入聚乙二醇（分子量20000；3毫渗摩尔·千克⁻¹）会导致黏膜流入持续逆转；只有从黏膜林格溶液中去除聚乙二醇才能恢复流入。该组织能逆着200 mM甘油的渗透梯度吸收水。上述数据已被纳入一个新模型，以解释该上皮组织的等渗液体流动。主要特点是，侧向细胞间隙黏膜边界的水力传导率（Lp）约为1×10⁻⁸厘米·秒⁻¹·厘米水柱⁻¹。这个Lp过低，无法以观察到的速率维持从侧向细胞间隙流出的液体的等渗性。从侧向细胞间隙流出的高渗液体被黏膜下层高渗性产生的跨细胞水流以及溶质通过黏膜分流通道的反向扩散所稀释。
