Scott D, Coleman P J, Mason R M, Levick J R
Department of Physiology, St George's Hospital Medical School, London SW17 0RE, UK.
J Physiol. 2000 Nov 1;528(Pt 3):609-18. doi: 10.1111/j.1469-7793.2000.00609.x.
Hyaluronan (HA), an anionic polysaccharide of synovial fluid, attenuates fluid loss from joints as joint pressure is raised ('outflow buffering'). The buffering is thought to depend on the expanded molecular domain of the polymer, which causes reflection by synovial extracellular matrix, leading to flow-dependent concentration polarization. We therefore assessed the effects of polysaccharides of differing average molecular volume and charge. Trans-synovial fluid drainage( 8d s) was measured at controlled joint fluid pressure (Pj) in knees of anaesthetized rabbits. The joints were infused with polydisperse HA of weight-average mass 2100 kDa (4 mg x ml(-1), n = 17), with polydisperse neutral dextran of similar average mass (2000 kDa; n = 7) or with Ringer solution vehicle (n = 2). The role of polymer charge was assessed by infusions of neutral or sulphated dextran of average molecular mass 500 kDa (n = 6). When HA was present, 8d s increased little with pressure, forming a virtual plateau of approximately 4 microl x min(-1) from 10 to 25 cmH2O. Neutral dextran 2000 failed to replicate this effect. Instead, 8d s increased steeply with Pj, reaching eight times the HA value by 20 cmH2O (P = 0.0001, ANOVA). Dextran 2000 reduced flows in comparison with Ringer solution. Analysis of the aspirated joint fluid showed that 31 +/- 0.07 % (s.e.m.) of dextran 2000 in the filtrand was reflected by synovium, compared with > or = 79 % for HA. The viscometric molecular radius of the dextran, approximately 31 nm, was smaller than that of HA (101-181 nm), as was its osmotic pressure. Anionic dextran 500 failed to buffer fluid drainage, but it reduced fluid escape and synovial conductance d 8d s/dPj more than neutral dextran 500 (P < 0.0001, ANOVA). The anionic charge increased the molecular volume and viscosity of dextran 500. The results support the hypothesis that polymer molecular volume influences its reflection by interstitial matrix and outflow buffering. Polymer charge influences flow through an effect on viscosity and possibly electrostatic interactions with negatively charged interstitial matrix.
透明质酸（HA）是滑液中的一种阴离子多糖，当关节压力升高时，它可减少关节内的液体流失（“流出缓冲”）。这种缓冲作用被认为取决于聚合物扩展的分子结构域，该结构域会引起滑膜细胞外基质的反射，导致与流量相关的浓度极化。因此，我们评估了不同平均分子体积和电荷的多糖的作用。在麻醉兔的膝关节中，于可控的关节液压力（Pj）下测量经滑膜的液体引流（8d s）。向关节内注入重均质量为2100 kDa的多分散HA（4 mg·ml⁻¹，n = 17）、平均质量相似的多分散中性葡聚糖（2000 kDa；n = 7）或林格氏液载体（n = 2）。通过注入平均分子量为500 kDa的中性或硫酸化葡聚糖（n = 6）来评估聚合物电荷的作用。当存在HA时，8d s随压力增加很少，在10至25 cmH₂O范围内形成了约4 μl·min⁻¹的虚拟平台。2000 kDa的中性葡聚糖未能重现这种效果。相反，8d s随Pj急剧增加，到20 cmH₂O时达到HA值的八倍（P = 0.0001，方差分析）。与林格氏液相比，2000 kDa的葡聚糖减少了流量。对抽取的关节液分析表明，滤过液中31±0.07%（标准误）的2000 kDa葡聚糖被滑膜反射，而HA的反射率≥79%。葡聚糖的粘度测定分子半径约为31 nm，小于HA的（101 - 181 nm），其渗透压也较小。500 kDa的阴离子葡聚糖未能缓冲液体引流，但它比500 kDa的中性葡聚糖更能减少液体渗出和滑膜电导d 8d s/dPj（P < 0.0001，方差分析）。阴离子电荷增加了500 kDa葡聚糖的分子体积和粘度。结果支持了聚合物分子体积影响其被间质基质反射和流出缓冲的假说。聚合物电荷通过对粘度的影响以及可能通过与带负电荷的间质基质的静电相互作用来影响流量。
