Ying X, Qiao R, Ishikawa S, Bhattacharya J
St. Luke's-Roosevelt Hospital Center, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York 10019.
J Appl Physiol (1985). 1994 Sep;77(3):1294-302. doi: 10.1152/jappl.1994.77.3.1294.
We used a microinjection approach to assess hydraulic properties of lung perimicrovascular adventitia (interstitial cuff surrounding microvessels). Isolated blood-perfused rat lungs held at constant airway pressure were microscopically viewed to identify subpleural venules (20 microns diam). Venular adventitia were microinjected with 20 nl of fluorescent albumin (4 g/dl), and then adventitial fluorescence was quantified at the injection site by either photometery or imaging. Nonlinear decay of adventitial fluorescence indicated liquid flux from the injection site into normal interstitium. In some experiments, we determined that the adventitial fluorescence flowed longitudinally along the venule length and filled single lymphatics. The fluorescence decay at the injection site was best described by equations of convective but not diffusive transport. The decay time constant (time to 37% initial), which relates inversely to hydraulic conductivity, increased 10-fold above baseline on lung expansion with airway pressure from 5 to 15 cmH2O (P < 0.05). However, presence or absence of blood flow, increase in filtration pressure, and tissue edema were all without effect on the time constant. Our estimate of the lower limit of baseline adventitial hydraulic conductivity was 5 x 10(-6) ml.cm-2.s-1.cmH2O-1. We conclude that hydraulic conductivity of perimicrovascular adventitia is not augmented by edema but that it is decreased by lung expansion.
我们采用微量注射法评估肺微血管周围外膜（围绕微血管的间质袖带）的水力学特性。在恒定气道压力下保持离体血液灌注的大鼠肺，通过显微镜观察以识别胸膜下小静脉（直径20微米）。向小静脉外膜微量注射20 nl荧光白蛋白（4 g/dl），然后通过光度测定法或成像在注射部位对血管外膜荧光进行定量。血管外膜荧光的非线性衰减表明液体从注射部位流入正常间质。在一些实验中，我们确定血管外膜荧光沿小静脉长度纵向流动并充满单个淋巴管。注射部位的荧光衰减最好用对流而非扩散传输方程来描述。衰减时间常数（降至初始值37%的时间）与水力传导率成反比，当气道压力从5 cmH2O增加到15 cmH2O使肺扩张时，该常数比基线增加了10倍（P < 0.05）。然而，有无血流、滤过压增加和组织水肿均对时间常数无影响。我们估计基线血管外膜水力传导率的下限为5×10(-6) ml·cm-2·s-1·cmH2O-1。我们得出结论，微血管周围外膜的水力传导率不会因水肿而增加，但会因肺扩张而降低。
