FLUID ABSORPTION BY RAT LUNG INSITU - PATHWAYS FOR SODIUM ENTRY IN THE LUMINAL MEMBRANE OF ALVEOLAR EPITHELIUM
FLUID ABSORPTION BY RAT LUNG INSITU - PATHWAYS FOR SODIUM ENTRY IN THE LUMINAL MEMBRANE OF ALVEOLAR EPITHELIUM
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DOI：
10.1113/jphysiol.1987.sp016457
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发表时间：
1987-03-01
影响因子：
5.5
通讯作者：
SAUMON, G
中科院分区：
文献类型：
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作者：
BASSET, G;CRONE, C;SAUMON, G
1. 本研究旨在探讨大鼠肺泡上皮腔膜及细胞旁通路的特征。实验采用交叉循环技术在肺原位灌注等渗缓冲林格液并灌注供体大鼠血液。2. 活性Na+转运速率为4.4 pmol/(cm2 s)。液体吸收量为156 nl/s，不受灌输液中蛋白质（166 nl/s）存在的影响。在没有Na+的情况下，流体吸收率为零。Amiloride （10-3 M）可减少60%的液体吸收。阿米洛利，加上d -葡萄糖的缺失，完全阻止了液体的吸收。管腔侧的连根素减少了液体吸收，而连根素没有影响。Amiloride和phloridzin （10-3 M）也阻止吸收。因此，钠离子在腔膜中有两种进入系统：钠离子通道和钠离子- d -葡萄糖同调。这些结果表明肺泡液的吸收是由于细胞活动。3. 用葡萄糖酸盐取代Cl-不仅停止了液体吸收，而且导致净流体运动的轻微逆转。4. 22Na+测定Na+的被动单向通量为9.9 pmol/(cm2 s)， 36Cl-测定Cl-的被动单向通量为12.4 pmol/(cm2 s)。这些通量是基于假设肺泡表面积为5000平方厘米。从这些数据中计算出的转移数与自由溶液中的转移数接近，表明存在中性或弱电荷的细胞间连接途径。d -甘露醇在细胞旁通路的通透性为1.7倍。可达厘米/秒。5. 在病理状态下，正常情况下Na+和Cl-的高反射系数降低，这是提出的流体吸收机制的结果。在这种情况下，肺水肿的发展取决于被动机械力和胶体渗透力的净平衡。6. 提出了出生时流体输送逆转的一种解释。
1. The purpose of the investigation was to characterize the luminal membrane and the paracellular pathway of rat lung alveolar epithelium. Experiments were performed on lungs in situ instilled with isotonic, buffered Ringer solution and perfused with blood from a donor rat using cross-circulation technique. 2. The rate of active Na+ transport was 4.4 pmol/(cm2 s). The fluid absorption was 156 nl/s, and was unaffected by the presence of protein in the instillate (166 nl/s). In the absence of Na+, fluid absorption was zero. Amiloride (10-3 M) reduced fluid absorption by 60%. Amiloride, combined with absence of D-glucose, arrested fluid absorption completely. Phloridzin at the luminal side reduced fluid absorption whilst phloretin had no effect. Amiloride together with phloridzin (10-3 M) also arrested absorption. Thus, there are two entry systems for Na+ in the luminal membrane: Na+ channels and a Na+-D-glucose symport. These results show that alveolar fluid absorption is due to cellular activity. 3. Substitution of Cl- with gluconate not only stopped fluid absorption, but led to slight reversal of net fluid movement. 4. Passive unidirectional flux of Na+, determined with 22Na+, was 9.9 pmol/(cm2 s) and that of Cl-, determined with 36Cl-, was 12.4 pmol/(cm2 s). These fluxes were based on an assumed alveolar surface area of 5000 cm2. Transference numbers calculated from these figures are close to those in free solution, suggesting a neutral or weakly charged intercellular junctional pathway. The D-mannitol permeability in the paracellular pathway was 1.7 .times. 10-8 cm/s. 5. It is a consequence of the proposed mechanism for fluid absorption that it becomes inoperative of the normally high reflexion coefficients of Na+ and Cl- are lowered in pathological states. In such conditions pulmonary oedema may develop depending on the net balance of passive mechanical and colloid-osmotic forces. 6. An explanation of the reversal of fluid transport at the time of birth is presented.