Dinno M A, Huang K C
Biochim Biophys Acta. 1978 May 18;509(2):318-25. doi: 10.1016/0005-2736(78)90050-0.
The effect of short circuit current on the unidirectional fluxes of ions transported across tight and leaky epithelia was investigated. It was found that short circuiting of the frog gastric mucosa (classified as a tight epithelium) caused a decease of the passive JClms and a significant increase of the net Cl- secretion. However, no significant change of H+ secretory rate was observed. On the other hand, short circuiting of the mouse intestine (a known leaky membrane) caused a simultaneous increase of both Jms and Jsm fluxes of Na+ while the net fluxes of Na+ and Cl- remained unchanged. Also, short circuiting did not change the water permeability of the mouse intestine. To explain some of these results a theoretical model is presented to demonstrate that while short circuiting can block the passive ionic movement, it will cause an increase in the energy consumption of the system and introduce certain important changes in the ionic barriers and e.m.fs. The simultaneous increase in the unidirectional fluxes of Na+ under short circuit conditions can best be explained by a decrease in the polarized nature of the transepithelial shunt, thereby increasing the diffusion coefficient of the ion(s). Such an increase is specially favorable to the Na+ rather than an anion.
研究了短路电流对跨紧密和泄漏上皮运输的离子单向通量的影响。发现青蛙胃黏膜（归类为紧密上皮）短路导致被动性跨黏膜氯通量（JClms）降低，净氯分泌显著增加。然而，未观察到氢离子分泌速率有显著变化。另一方面，小鼠肠道（已知的泄漏膜）短路导致钠的跨黏膜通量（Jms）和短路通量（Jsm）同时增加，而钠和氯的净通量保持不变。此外，短路并未改变小鼠肠道的水渗透性。为了解释其中一些结果，提出了一个理论模型，以证明虽然短路可以阻止被动离子移动，但它会导致系统能量消耗增加，并在离子屏障和电动势方面引入某些重要变化。短路条件下钠单向通量的同时增加，最好用跨上皮分流的极化性质降低来解释，从而增加离子的扩散系数。这种增加对钠特别有利，而不是对阴离子有利。
