Villegas R, Villegas G M, Blei M, Herrera F C, Villegas J
J Gen Physiol. 1966 Sep;50(1):43-59. doi: 10.1085/jgp.50.1.43.
The penetration of (14)C-labeled erythritol, mannitol, and sucrose through the axolemma was determined in medium sized paired axons, one at rest and the other stimulated 25 times per sec. The resting permeabilities, in 10(-7) cm/sec, are erythritol, 2.9 +/- 0.3 (mean +/- SEM); mannitol, 2.3 +/- 0.4; and sucrose 0.9 +/- 0.1. In the stimulated axons they are: erythritol, 5.2 +/- 0.3; mannitol, 4.0 +/- 0.5; and sucrose, 1.8 +/- 0.3. Thus, the calculated permeabilities during activity (1 msec per impulse), in the same units, are: 100, 75, and 38, respectively. These changes in permeability are reversible. The effects of external potassium and sodium concentrations on erythritol penetration were also studied. At rest, erythritol penetration is independent of potassium and sodium concentrations. In the stimulated axons, erythritol penetration decreases when the extracellular sodium is diminished. Sodium influx (not the efflux) decreases during rest and activity when the extracellular sodium is diminished. The diminution during activity of erythritol and sodium entries in low sodium solutions may be related to a decrease of a drag effect of sodium ions on the nonelectrolyte molecules or to independent effects of the sodium concentration on sodium influx and the nonelectrolyte pathways. The axolemma discriminates among erythritol, mannitol, sucrose, and the different ionic species during rest and activity.
在中等大小的成对轴突中测定了（14）C标记的赤藓糖醇、甘露醇和蔗糖通过轴膜的渗透率，其中一根轴突处于静息状态，另一根轴突每秒刺激25次。静息渗透率（单位为10^(-7)厘米/秒）分别为：赤藓糖醇，2.9±0.3（平均值±标准误）；甘露醇，2.3±0.4；蔗糖，0.9±0.1。在受刺激的轴突中，它们分别为：赤藓糖醇，5.2±0.3；甘露醇，4.0±0.5；蔗糖，1.8±0.3。因此，在活动期间（每个冲动1毫秒）以相同单位计算的渗透率分别为：100、75和38。这些渗透率的变化是可逆的。还研究了细胞外钾和钠浓度对赤藓糖醇渗透的影响。在静息时，赤藓糖醇的渗透与钾和钠浓度无关。在受刺激的轴突中，当细胞外钠减少时，赤藓糖醇的渗透会降低。当细胞外钠减少时，静息和活动期间钠的内流（而非外流）会减少。在低钠溶液中，活动期间赤藓糖醇和钠进入量的减少可能与钠离子对非电解质分子的拖曳效应降低有关，或者与钠浓度对钠内流和非电解质途径的独立影响有关。轴膜在静息和活动期间能够区分赤藓糖醇、甘露醇、蔗糖和不同的离子种类。
