Seo Y, Ammer U, Ishikawa T, Murakami M
Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
Jpn J Physiol. 1995;45(2):229-39. doi: 10.2170/jjphysiol.45.229.
The diffusion coefficient of an 19F-labelled organic acid (3-trifluoromethylhippurate: TFMH) was measured in intact human red blood cells (RBCs) and sealed right-side-out ghosts at 22.5 +/- 0.05 degrees C. Diffusion coefficients were measured using stimulated echo and spin-echo pulsed field gradient sequences. The apparent diffusion coefficient (Da) of TFMH in the intracellular space was much smaller than in the extracellular medium. This was due to restricted diffusion of intracellular TFMH since i) the intracellular Da decreased when the diffusion time was increased, and ii) the smaller Da component disappeared when the membrane was permeabilized with saponin. From the intracellular Da values obtained over a range of diffusion times, from 5 ms to 1 s, the apparent radius of the diffusion barrier was estimated to be 3 +/- 1.1 micron assuming spherical geometry. Despite the high protein concentration in the intracellular space of the intact RBC, the intracellular values of Da were similar to the values obtained in the ghosts at the same diffusion times. We therefore conclude that the small diffusion coefficient of intracellular TFMH is mainly explained by the restricted diffusion due to the cell boundary.
在22.5±0.05℃下，测量了19F标记的有机酸（3 - 三氟甲基马尿酸：TFMH）在完整人类红细胞（RBC）和外翻封接血影中的扩散系数。使用受激回波和自旋回波脉冲场梯度序列测量扩散系数。TFMH在细胞内空间的表观扩散系数（Da）远小于细胞外介质中的表观扩散系数。这是由于细胞内TFMH的扩散受限，原因如下：i）当扩散时间增加时，细胞内Da降低；ii）当用皂角苷使膜通透时，较小的Da组分消失。根据在5毫秒至1秒的一系列扩散时间内获得的细胞内Da值，假设为球形几何形状，估计扩散屏障的表观半径为3±1.1微米。尽管完整红细胞的细胞内空间蛋白质浓度很高，但在相同扩散时间下，细胞内Da值与血影中获得的值相似。因此，我们得出结论，细胞内TFMH的小扩散系数主要是由细胞边界导致的扩散受限所解释。
