[Effects of age on filtration coefficient in isolated zone 3 rat perfused lungs]

To investigate the effect of age on the filtration coefficient (Kf) in isolated rat perfused lungs, we divided 18 Sprague-Dawley rats randomly into 3 groups; 1) 5 wk of age, 150 +/- 1.5g, n = 6; 2) 10 wk of age, 320 +/- 18.8g, n = 6; and 3) 14 wk of age, 460 +/- 10.0g, n = 6. We used Krebs-Henseleit solution with 5% bovine serum albumin as the perfusate and maintained perfusion using constant pressure circuit system. We calculated the filtration coefficient in isolated rat perfused lungs in zone 3 conditions (pulmonary arterial pressure > pulmonary venous pressure > alveolar pressure) using gravimetric method. The filtration coefficients in rats of 14 wk of age were 3-fold higher than those in other two groups (Kf = 5.31 +/- 0.29 mg.min-1.cmH2O-1.g-1 in 5 wk of age, 5.38 +/- 0.49 mg.min-1.cmH2O-1.g-1 in 10 wk of age and 16.17 +/- 0.46 mg.min-1.cmH2O-1.g-1 in 14 wk of ages). Also, there were a large population of leukocytes in lung of 14 wk of age, but not in 5 wk and 10 wk of age. In addition, the filtration coefficients in 5 wk and 10 wk of age were of the same magnitude as in other investigators' reports. We conclude that rat in 10 wk of age is suitable for the evaluation of the pulmonary vascular permeability.