Fischbarg J, Liebovitch L S, Koniarek J P
Biochim Biophys Acta. 1987 Apr 23;898(3):266-74. doi: 10.1016/0005-2736(87)90066-6.
On the basis of evidence derived mostly from human erythrocytes, it has been suggested that water traverses cell membranes through membrane-spanning proteins such as the anion channel or the glucose transporter acting as water pores. However, specific inhibitors of such permeation processes have not been found to block water transport, and hence a precise identification of the water route has not been possible so far. We have investigated this issue by characterizing the osmotic flows across a fluid-transporting epithelium, the rabbit corneal endothelium. The rate of such flows was monitored continuously as a function of time. We confirmed prior findings of an inhibition by PCMBS on osmotic water flow, and lack of inhibition by DTNB and DIDS. On the other hand, we have found for the first time that several blockers of glucose facilitated diffusion, namely, phloretin (2 mM), phloridzin (2 mM), diallyldiethylstilbestrol (0.1 mM), cytochalasin B (20 micrograms/ml), and ethylidene-D-glucose (200 mM), all clearly inhibit osmotic flow. Our evidence is consistent with the hypothesis that both water and glucose may traverse these cell membranes through the same channel-like pathway contained in the glucose transporter membrane-spanning protein.
基于主要来自人体红细胞的证据，有人提出水通过跨膜蛋白（如阴离子通道或作为水孔的葡萄糖转运蛋白）穿过细胞膜。然而，尚未发现此类渗透过程的特异性抑制剂能阻断水的运输，因此到目前为止，还无法精确确定水的运输途径。我们通过表征兔角膜内皮这种液体运输上皮的渗透流来研究这个问题。这种流率作为时间的函数被连续监测。我们证实了之前关于对氯汞苯甲酸抑制渗透水流以及二硫代硝基苯甲酸和二异丁基氨基磺酸钠不产生抑制作用的发现。另一方面，我们首次发现几种葡萄糖易化扩散的阻滞剂，即根皮素（2 mM）、根皮苷（2 mM）、二烯丙基二乙基己烯雌酚（0.1 mM）、细胞松弛素B（20微克/毫升）和亚乙基-D-葡萄糖（200 mM），都能明显抑制渗透流。我们的证据与水和葡萄糖可能通过葡萄糖转运蛋白跨膜蛋白中包含的相同通道样途径穿过这些细胞膜的假设一致。
