Lundbaek J A, Hansen A J
Department of General Physiology and Biophysics, Panum Institute, University of Copenhagen, Denmark.
Acta Physiol Scand. 1992 Dec;146(4):473-84. doi: 10.1111/j.1748-1716.1992.tb09449.x.
The micro-electrode method for determination of interstitial volume fraction (alpha) (Nicholson & Phillips 1981), was evaluated. The extracellular marker, tetramethylammonium+, is iontophoretically ejected from a micropipette and the change in concentration measured at a distance by an ion-sensitive micro-electrode and fitted to a diffusion equation. We used suspensions of human red blood cells as a model system and found that the values of alpha determined by this method and by haematocrit measurement were linearly correlated (r = 0.94) and not significantly different. The micro-electrode method was used to characterize the interstitial space in rat brain cortex during normal conditions and during arrest of blood flow supply. Transport of solutes in interstitial space is governed by two characteristics, the interstitial volume fraction and the tortuosity factor. During control conditions, the interstitial volume fraction was 0.18 +/- 0.02 (mean +/- SEM), whereas it decreased to 0.07 +/- 0.01 in ischaemia. The tortuosity factor was 1.40 +/- 0.05 in controls and increased to 1.63 +/- 0.09 during ischaemia. Our measurements support the validity of the micro-electrode method (Nicholson & Phillips 1981) and demonstrate that arrest of blood supply changes interstitial diffusional characteristics of brain cortex mainly by diminishing the size of the interstitial diffusional space.
对用于测定组织间隙体积分数（α）的微电极方法（Nicholson和Phillips，1981年）进行了评估。细胞外标记物四甲基铵离子（tetramethylammonium⁺）通过微吸管进行离子电泳喷射，并通过离子敏感微电极在一定距离处测量浓度变化，并将其拟合到扩散方程中。我们使用人类红细胞悬液作为模型系统，发现通过该方法测定的α值与通过血细胞比容测量得到的值呈线性相关（r = 0.94），且无显著差异。微电极方法用于表征正常条件下和血流供应停止期间大鼠大脑皮层的组织间隙空间。溶质在组织间隙中的转运受两个特征的支配，即组织间隙体积分数和迂曲因子。在对照条件下，组织间隙体积分数为0.18±0.02（平均值±标准误），而在缺血时降至0.07±0.01。对照中迂曲因子为1.40±0.05，缺血时增加至1.63±0.09。我们的测量结果支持微电极方法（Nicholson和Phillips，1981年）的有效性，并表明血液供应停止主要通过减小组织间隙扩散空间的大小来改变大脑皮层的组织间隙扩散特性。
