Lahajnar G, Macek P, Zupancic I
Jozef Stefan Institute, Ljubljana, Slovenia.
Bioelectrochemistry. 2000 Dec;52(2):179-85. doi: 10.1016/s0302-4598(00)00100-8.
The inhibitory effect of a series of neutral lipophilic solutes (methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-amylalcohol, n-hexanol, diethylether, nitrobenzene, and pyridine) on the diffusional water permeability (Pd, tot) of bovine erythrocyte membrane at 25 degrees C was studied in comparison to that of p-chloromercuri benzoate (pCMB). Permeability data were obtained by measuring the transmembrane diffusional water exchange time tau(exch) using an 1H-T2 NMR technique. Maximal inhibition by approximately 50% of Pd, tot was produced by 2 mM pCMB which completely blocked the membrane water channels in 20 min, hence suggesting the channel-to-lipid diffusional water permeability ratio of about 1:1. Furthermore, the maximal inhibitory effect of pCMB in combination with the lipophilic solutes was lower than that of pCMB alone. As pCMB does not interfere with the lipid bilayer, and provided that it blocks the water channels in solute presence as well, this confirms that the solutes induce an increase in the lipid-mediated background water permeability contribution (Pd, lipid) by the formation of aqueous leaks in the membrane hydrophobic barrier. However, faster but less efficient in permeability inhibition than pCMB (either alone or combined with solutes) were the lipophilic solutes alone. Taken together, the results indicate that the lipophilic solutes suppress the membrane total permeability Pd, tot by two opposing effects: a reduction of its channel-mediated part (Pd, channel) to the extent exceeding that of a simultaneous Pd, lipid increase. The inhibitory potency of the solutes tested appears to be correlated with their solubility in the membrane medium.
研究了一系列中性亲脂性溶质（甲醇、乙醇、正丙醇、异丙醇、正丁醇、异戊醇、正己醇、二乙醚、硝基苯和吡啶）在25℃时对牛红细胞膜扩散水渗透率（Pd,tot）的抑制作用，并与对氯汞苯甲酸（pCMB）进行了比较。通过使用1H-T2 NMR技术测量跨膜扩散水交换时间tau(exch)来获得渗透率数据。2 mM pCMB可使Pd,tot最大抑制约50%，并在20分钟内完全阻断膜水通道，因此表明通道与脂质的扩散水渗透率之比约为1:1。此外，pCMB与亲脂性溶质联合使用时的最大抑制作用低于单独使用pCMB时。由于pCMB不干扰脂质双层，并且假设它在溶质存在时也能阻断水通道，这证实了溶质通过在膜疏水屏障中形成水渗漏来诱导脂质介导的背景水渗透率贡献（Pd,lipid）增加。然而，单独的亲脂性溶质在渗透率抑制方面比pCMB（单独或与溶质联合使用）更快但效率更低。综上所述，结果表明亲脂性溶质通过两种相反的作用抑制膜总渗透率Pd,tot：降低其通道介导部分（Pd,channel），其程度超过同时增加的Pd,lipid。所测试溶质的抑制效力似乎与其在膜介质中的溶解度相关。
