HYDRAULIC CONDUCTIVITY OF ISCHEMIC PULMONARY VENULES

We report the first determination of lung endothelial barrier properti es in ischemic, nonreperfused microvessels. We quantified the endothel ial barrier in terms of hydraulic conductivity (L(p)) in single pulmon ary venules (diameter 20-50 mum) of isolated blood perfused lungs (dog , rat), held at constant inflation pressure (5 cmH2O) with a gas mixtu re containing 21 % oxygen. L(p) were determined by our split-drop tech nique in which an oil drop is first microinjected into a venule and th en split by microinjection of a protein solution. L(p) was interpreted from measurements of the rate of oil drop movement. Baseline L(p) rec orded in the first 30 min of perfusion averaged 3.4 +/- 0.9 X 10(-7) M l/(cm2.s.cmH2O). Then, in two separate groups of venules in which we e stablished 1.3 +/- 0.1 h and 3.4 +/- 0.8 h of ischemia, we determined L(p) which were, respectively, 145 +/- 6.5 and 308 +/- 13% above basel ine (P < 0.05). We conclude that ischemia alone, in the absence of rep erfusion, significantly deteriorates the lung endothelial barrier.