Segmental microvascular permeability in ischemia-reperfusion injury in rat lung

Segmental microvascular permeabilities were measured using pre- and postalveolar vessel capillary filtration coefficient ( K ) values (ml ⋅ min ⋅ cmH O ⋅ 100 g ) in isolated rat lungs subjected to ischemia-reperfusion (I/R). Total K values measured in flowing and nonflowing lungs were highly correlated ( r = 0.98, P < 0.0001). K values were then measured in another group of lungs under no-flow conditions when airway pressure was increased to 20 cmH O and either the arterial or venous pressure was elevated to 7-8 cmH O to measure the prealveolar and postalveolar K values. Control total and postalveolar K values were 0.0225 ± 0.001 and 0.0219 ± 0.001 ml ⋅ min ⋅ cmH O ⋅ 100 g , respectively, and the prealveolar permeability was extremely small (0.00003 ± 0.00005 ml ⋅ min ⋅ cmH O ⋅ 100 g ). K values were again made in nonflowing lungs that had been subjected to 45 min of ischemia followed by 30 min of reperfusion. After I/R, the total membrane K increased 10-fold to 0.2597 ± 0.006 ml ⋅ min ⋅ cmH O ⋅ 100 g , the prealveolar K increased to 0.0677 ± 0.003 ml ⋅ min ⋅ cmH O ⋅ 100 g , and the postalveolar K increased to 0.1354 ± 0.008 ml ⋅ min ⋅ cmH O ⋅ 100 g ( P < 0.05 for all I/R values). These data indicate that normal solvent microvascular permeability was predominantly postalveolar, and after I/R damage, the postalveolar (venular) permeability comprised 52% of the total, whereas the prealveolar and alveolar vessels comprised only 27 and 23%, respectively, of the total K .