Garcia A M, Frank E H, Grimshaw P E, Grodzinsky A J
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139, USA.
Arch Biochem Biophys. 1996 Sep 15;333(2):317-25. doi: 10.1006/abbi.1996.0397.
We have studied the contributions of diffusion, fluid flow and electrical migration to molecular transport through adult articular cartilage explants using neutral and charged solutes that were either radiolabeled (3H2O, [35S]sulfate, [3H]thymidine, [3H]raffinose, and a synthetic matrix metalloproteinase inhibitor) or fluorescently tagged (NSPA and Lissamine-dextran). In order to induce fluid flow within the cartilage matrix without mechanical deformation, electric current densities were applied across cartilage disks. These currents produced electroosmotic fluid velocities of 1-2 microns/s, magnitudes that have been reported to exist during joint loading in vivo. This fluid convection enhanced neutral solute flux relative to passive diffusion alone by a factor that increased with the size of the solute. While the enhancement factor for 3H2O was 2.3-fold, that for [3H]raffinose (594 Da) and similar sized neutral solutes was 10-fold, suggesting that the effect of fluid flow is important even for small solutes. The largest enhancement (25-fold) was seen for the neutral 10-kDa Lissamine-dextran, confirming that fluid convection is most important for large solutes. We also studied the electrophoretic contribution to solute flux, which is relevant to the presence of intratissue streaming potentials induced during loading in vivo. Using the negatively charged [35S]sulfate ion with a range of current densities, as much as a 10-fold enhancement in flux was observed. Values for the intrinsic transport properties of the solutes (e.g., diffusivity, electrical mobility, hydrodynamic hindrance factor) can be obtained from the data.
我们使用放射性标记（3H2O、[35S]硫酸盐、[3H]胸腺嘧啶核苷、[3H]棉子糖和一种合成基质金属蛋白酶抑制剂）或荧光标记（NSPA和 Lissamine-葡聚糖）的中性和带电溶质，研究了扩散、流体流动和电迁移对分子通过成年关节软骨外植体运输的贡献。为了在不产生机械变形的情况下在软骨基质内诱导流体流动，在软骨圆盘上施加电流密度。这些电流产生了1-2微米/秒的电渗流体速度，该速度大小在体内关节加载过程中已有报道。这种流体对流相对于单独的被动扩散增强了中性溶质通量，增强因子随溶质大小增加而增大。对于3H2O，增强因子为2.3倍，对于[3H]棉子糖（594 Da）和类似大小的中性溶质，增强因子为10倍，这表明即使对于小溶质，流体流动的影响也很重要。对于中性的10-kDa Lissamine-葡聚糖，观察到最大增强（25倍），证实流体对流对大溶质最为重要。我们还研究了电泳对溶质通量的贡献，这与体内加载过程中诱导的组织内流动电位的存在有关。使用带负电荷的[35S]硫酸根离子和一系列电流密度，观察到通量增强高达10倍。溶质的固有传输特性值（例如，扩散率、电迁移率、流体动力学阻碍因子）可以从数据中获得。
