利用哇巴因、依他尼酸和代谢抑制剂对兔胆囊上皮细胞两种转运机制进行功能区分。

Functional distinction between two transport mechanisms in rabbit gall-bladder epithelium by use of ouabain, ethacrynic acid and metabolic inhibitors.

作者信息

Frederiksen O

出版信息

J Physiol. 1978 Jul;280:373-87. doi: 10.1113/jphysiol.1978.sp012389.

DOI:10.1113/jphysiol.1978.sp012389

PMID:690888

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1282664/

Abstract

Net fluid transport rate, transepithelial p.d. and resistance, and unidirectional Na+-fluxes were measured in rabbit gall-bladder preparations exposed on both sides to bicarbonate-Ringer solution in vitro. 2. Both ouabain and ethacrynic acid (ETCA) caused dose-dependent decreases of net fluid transport rate; ouabain inhibited fluid transport predominantly from the serosal side, whereas the inhibitory effect of ETCA was elicited mainly from the mucosal (luminal) side. Applied bilaterally, the ID50 for ouabain was 2.5 X 10(-6) M, and for ETCA 2.3 X 10(-4) M. After maximal inhibition at each concentration level of the two inhibitors fluid transport could not be reversed. 3. 2,4-Dinitrophenol (2,4-DNP) (2 X 10(-4) M) or substitution of O2 by N2 caused an 80% reversible decrease of net fluid transport. 4. The spontaneous p.d. across the rabbit gall-bladder was about 2.7 mV, mucosal side positive. 2,4-DNP, N2 and serosal application of ouabain depressed the p.d. after an initial hyperpolarization. This decrease was reversible during recovery from 2,4-DNP and N2, but irreversible after removal of ouabain at concentrations greater than or equal to 10(-4) M. Mucosal application of ETCA (10(-3) M) caused no decrease in p.d., which actually increased slightly. 5. Calculated passive serosal-to-mucosal Na+-fluxes changed in the same direction as did changes in conductance. 6. It is concluded that ETCA does not interfere primarily with the Na-K-ATPase or cellular oxidative metabolism. The data support the proposal that the pump responsible for isosmotic transepithelial fluid transfer is located in the luminal end of the cells. This pump is ETCA-sensitive. The ATPase-dependent Na-K pump, which can be inhibited by ouabain, is localized in the serosa-facing cell membrane. The data suggest that the inhibition of net fluid transport by ouabain is indirect and mediated by changes in intracellular ion concentrations. 7. The results support the concept that the transepithelial fluid transport mechanism is electroneutral, and suggest that the mucosa positive transepithelial p.d. is due to differences in electromotive forces arising from ion (mainly K+) diffusion across the mucosal and serosal cell membranes.

摘要

在体外将兔胆囊标本两侧暴露于碳酸氢盐 - 林格液中，测量其净液体转运速率、跨上皮电位差和电阻以及单向钠通量。2. 哇巴因和依他尼酸（ETCA）均引起净液体转运速率呈剂量依赖性下降；哇巴因主要从浆膜侧抑制液体转运，而ETCA的抑制作用主要从黏膜（管腔）侧引发。双侧应用时，哇巴因的半数抑制浓度（ID50）为2.5×10⁻⁶ M，ETCA为2.3×10⁻⁴ M。在两种抑制剂的每个浓度水平达到最大抑制后，液体转运无法逆转。3. 2,4 - 二硝基苯酚（2,4 - DNP）（2×10⁻⁴ M）或用N₂替代O₂导致净液体转运可逆性下降80%。4. 兔胆囊的自发电位差约为2.7 mV，黏膜侧为正。2,4 - DNP、N₂以及浆膜侧应用哇巴因在初始超极化后使电位差降低。从2,4 - DNP和N₂恢复过程中这种降低是可逆的，但在去除浓度大于或等于10⁻⁴ M的哇巴因后是不可逆的。黏膜侧应用ETCA（10⁻³ M）未导致电位差降低，实际上略有升高。5. 计算得出的被动性从浆膜到黏膜的钠通量变化方向与电导变化方向相同。6. 得出结论，ETCA主要不干扰钠 - 钾 - ATP酶或细胞氧化代谢。数据支持负责等渗跨上皮液体转运的泵位于细胞管腔端的提议。该泵对ETCA敏感。可被哇巴因抑制的依赖ATP酶的钠 - 钾泵位于面向浆膜的细胞膜上。数据表明哇巴因对净液体转运的抑制是间接的，由细胞内离子浓度变化介导。7. 结果支持跨上皮液体转运机制是电中性的概念，并表明黏膜侧为正的跨上皮电位差是由于离子（主要是K⁺）跨黏膜和浆膜细胞膜扩散产生的电动势差异所致。