Levick J R, Knight A D
Department of Physiology, St. George's Hospital Medical School, London, United Kingdom.
Microvasc Res. 1988 Jan;35(1):109-21. doi: 10.1016/0026-2862(88)90054-4.
Fluid exchanges between blood and a synovial joint cavity across two membranes in series--synovial capillary wall (fenestrated) and synovial intima (modified connective tissue). The relation between transsynovial absorption of intraarticular Krebs solution (flow Qs) and plasma colloid osmotic pressure pi p was investigated in rabbit knees perfused at constant blood pressure. Intraarticular pressure Pj was independently controlled. Linear relations between transsynovial flow and plasma colloid osmotic pressure established that transsynovial flow obeys the Starling hypothesis. However osmotic conductance, dQs/d pi p, increased 3.9 times when Pj was raised from 6 cm H2O or subatmospheric pressure to 18 cm H2O--the "yield phenomenon." Comparison of the effects of pi p and capillary pressure revealed no major change in the osmotic reflection coefficient of the blood-joint barrier to albumin upon raising Pj. The large increase in osmotic conductance was predicted quantitatively by a previous model (prediction 3.8 X) based on increases in extravascular (intimal) conductance as a function of extravascular pressure. It is argued that capillary endothelium is not the sole significant hydraulic resistance in this pathway. In the terminology of Intaglietta and de Plomb (1973) synovial capillaries are functionally intermediate between "tubes" and "tunnels."
血液与滑膜关节腔之间的液体交换通过两层串联的膜进行——滑膜毛细血管壁（有窗孔）和滑膜内膜（改良的结缔组织）。在以恒定血压灌注的兔膝关节中，研究了关节内克雷布斯溶液的经滑膜吸收（流量Qs）与血浆胶体渗透压πp之间的关系。关节内压力Pj是独立控制的。经滑膜流量与血浆胶体渗透压之间的线性关系表明经滑膜流量符合斯塔林假说。然而，当Pj从6 cm H₂O或低于大气压升高到18 cm H₂O时，渗透传导率dQs/dπp增加了3.9倍——即“屈服现象”。比较πp和毛细血管压力的影响发现，升高Pj后，血液-关节屏障对白蛋白的渗透反射系数没有重大变化。基于血管外（内膜）传导率随血管外压力增加的情况，先前的一个模型（预测值为3.8倍）对渗透传导率的大幅增加进行了定量预测。有人认为，毛细血管内皮不是该途径中唯一重要的水力阻力。用因塔列塔和德普洛姆（1973年）的术语来说，滑膜毛细血管在功能上介于“管道”和“隧道”之间。
