Lucas V A, Duncan G
Exp Eye Res. 1983 Aug;37(2):175-82. doi: 10.1016/0014-4835(83)90076-3.
The unidirectional fluxes (influx and efflux) of glucose across frog lens membranes were investigated using the radio-labelled sugar analogue 3-O-methyl-D-[U-14C]glucose. The effect of various inhibitors of sugar transport on the movement of 3-O-methylglucose was studied and the specificity of the inhibition was estimated by carrying out concomitant measurements of lens sodium content. The movement of 3-O-methylglucose into the lens was rapid, and 50% equilibration occurred within 5 hr. The influx was reduced in the presence of phloretin, phloridzin, ouabain, iodoacetate and cytochalasin B, but only in the case of the latter was there no concomitant change in lens sodium content. Only cytochalasin B can therefore be regarded as a specific inhibitor of glucose transport. The efflux of 3-O-methylglucose was followed after 16 hr incubation with [14C]3-O-methylglucose. The efflux kinetics had a double exponential form and the half-time of the slower phase was 165 mins. The efflux of the slow phase was found to be sensitive to the presence of inhibitors. Phloretin and cytochalasin B produced the most marked reduction in efflux rate, but again only in the latter case was the effect reversible. Bidirectional transport of glucose therefore occurs in the lens and movement in both directions is reduced by cytochalasin B, which appears to be the only inhibitor of transport so far studied that does not disturb lens ion levels.
利用放射性标记的糖类似物3 - O - 甲基 - D - [U - 14C]葡萄糖，研究了葡萄糖跨蛙晶状体膜的单向通量（流入和流出）。研究了各种糖转运抑制剂对3 - O - 甲基葡萄糖转运的影响，并通过同时测量晶状体钠含量来评估抑制的特异性。3 - O - 甲基葡萄糖进入晶状体的速度很快，5小时内达到50%的平衡。在根皮素、根皮苷、哇巴因、碘乙酸盐和细胞松弛素B存在的情况下，流入量减少，但只有在细胞松弛素B存在时，晶状体钠含量才没有伴随变化。因此，只有细胞松弛素B可被视为葡萄糖转运的特异性抑制剂。在用[14C]3 - O - 甲基葡萄糖孵育16小时后，追踪3 - O - 甲基葡萄糖的流出情况。流出动力学呈双指数形式，较慢相的半衰期为165分钟。发现较慢相的流出对抑制剂的存在敏感。根皮素和细胞松弛素B使流出速率降低最为显著，但同样只有在细胞松弛素B的情况下，这种作用才是可逆的。因此，葡萄糖在晶状体中进行双向转运，并且细胞松弛素B会降低双向的转运，细胞松弛素B似乎是迄今为止研究的唯一一种不会干扰晶状体离子水平的转运抑制剂。
