OSMOTIC REFLECTION COEFFICIENTS OF CAPILLARY WALLS TO LOW-MOLECULAR WEIGHT HYDROPHILIC SOLUTES MEASURED IN SINGLE PERFUSED CAPILLARIES OF FROG MESENTERY
OSMOTIC REFLECTION COEFFICIENTS OF CAPILLARY WALLS TO LOW-MOLECULAR WEIGHT HYDROPHILIC SOLUTES MEASURED IN SINGLE PERFUSED CAPILLARIES OF FROG MESENTERY
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DOI：
10.1113/jphysiol.1976.sp011561
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发表时间：
1976-01-01
影响因子：
5.5
通讯作者：
MICHEL, CC
中科院分区：
文献类型：
--
作者：
CURRY, FE;MASON, JC;MICHEL, CC
用人红细胞在含有1.0 g白蛋白/100 ml的蛙林格氏溶液中的悬浮液灌注透照蛙肠系膜的单个毛细血管。肠系膜外表面用正常蛙林格氏溶液和通过加入以下溶质之一制成高渗的蛙林格氏溶液洗涤：NaCl（100 mmol 1-1）;尿素（100 mmol 1 -1）;蔗糖（20-50 mmol 1 - 1）;氰钴胺（8.5 mmol 1-1）。肠系膜温度在14 - 16 ℃之间。C在所有实验中用正常林格氏液灌流肠系膜，在一系列已知的毛细血管压力下，通过测量穿过毛细血管壁的液体过滤速率来确定过滤系数。过滤系数从0.69 × 10 - 4变化到0.69 × 10 - 4。10-3-4.45 ×10-3μ m s-1H 2 O-1，平均值为1.87 ×10-3μ m s-1 cm H2O-1。当通过添加测试溶质使灌流液高渗时，渗透反射系数（σ）根据附加过滤速率、灌流液中供试溶质的浓度和过滤系数计算毛细血管壁对供试溶质的渗透率。σ的平均值NaCl，0.068 ±。0.03（3个毛细管）;尿素，0.071 ±。0.015（4个毛细管）;蔗糖，0.115 ±。0.023（7个毛细管）;氰钴胺，0.100 ±。0.03（3个毛细管）。在进一步的实验中，在同一毛细管中测定了对NaCl、尿素和蔗糖的渗透反射系数。进行了五个技术上可接受的实验。尽管σ的值存在差异，在不同的毛细管之间，在任何一个毛细管中σ的值。具有相同的量级，并且似乎没有与供试品溶质的分子大小相关的显著趋势。也许水和小的亲水性分子穿过毛细血管壁只有一条通道。结果可以解释为水的排他通道与水和小亲水分子共享的通道平行。唯一的水通道可以是内皮细胞的膜和细胞质，而共享通道可以位于细胞间连接处。结果表明，蛙肠系膜毛细血管的水通道占总过滤系数的10%左右。共享通道显示出对所研究的分子的相对较小的限制。在流体静压差和渗透压差为驱动力的条件下，对通过2个通道的体积流量进行估计。
Individual capillaries of the transilluminated frog mesentery were perfused with suspensions of human red cells in frog Ringer solution containing 1.0 g albumin/100 ml. The outer surface of the mesentery has been washed with normal frog Ringer solution and with frog Ringer solutions made hypertonic by addition of one of the following solutes: NaCl (100 mmol 1-1); urea (100 mmol 1-1); sucrose (20-50 mmol 1-1); cyanocobalamin (8.5 mmol 1-1). The temperature of the mesentery was between 14-16.degree. C in all experiments. With the mesentery superfused with normal Ringer, the filtration coefficient was determined from measurements of the rate of fluid filtration across the capillary wall, at a series of known capillary pressures. Filtration coefficient varied from 0.69 .times. 10-3-4.45 .times. 10-3 .mu.m s-1 H2O-1 with an average value of 1.87 .times. 10-3 .mu.m s-1 cm H2O-1. When the superfusate was made hypertonic by the addition of a test solute, the osmotic reflection coefficient (.sigma.) of the capillary wall to test solute was calculated from the additional rate of filtration, the concentration of test solute in the superfusate and the filtration coefficient. Average values for .sigma. were: NaCl, 0.068 .+-. 0.03 (3 capillaries); urea, 0.071 .+-. 0.015 (4 capillaries); sucrose, 0.115 .+-. 0.023 (7 capillaries); cyanocobalamin, 0.100 .+-. 0.03 (3 capillaries). In further experiments, the osmotic reflection coefficients to NaCl, urea and sucrose were determined in the same capillary. Five technically acceptable experiments were carried out. Although there were differences in the value of .sigma. between different capillaries, in any one capillary values of .sigma. were of the same magnitude and there appeared to be no significant trend with the molecular size of the test solute. Perhaps there is a single pathway for water and small hydrophilic molecules across the capillary wall. The results may be interpreted in terms of an exclusive channel for water in parallel with a channel shared by both water and small hydrophilic molecules. The exclusive water channel may be the membranes and cytoplasm of the endothelial cells and the shared channel may be located in the intercellular junctions. The data suggest the exclusive water channel represents about 10% of the total filtration coefficient in frog mesenteric capillaries. The shared channel shows relatively little restriction to the molecules investigated. Estimates of the volume flow through the 2 channels are made for conditions where hydrostatic pressure differences and osmotic pressure differences are the driving forces.