Isolated Perfused Rat Lung Model

Sprague-Dawley male rats weighing 350 ± 20 g were handled according to the guidelines of the National Institutes of Health; all animal experiments were approved by the Animal Review Committee of the National Defense Medical Center (Permit Number: IACUC-18-218). Rat lungs were isolated and perfused in the chest as previously described (Chu et al., 2002; Wu et al., 2015; Wu et al., 2017). Briefly, after tracheotomy, the rats were ventilated with air containing 5% CO₂ at 60 breaths/min at a tidal volume of 3 ml with a positive end-expiratory pressure of 1 cm H₂O. A sternotomy was performed, heparin was injected into the right ventricle, and approximately 10 ml intracardiac blood was collected. The pulmonary artery was cannulated, and a drainage cannula was placed in the left ventricle. The cannulae were connected to the perfusion circuit and perfused with physiological salt solution (119 mM NaCl, 4.7 mM KCl, 1.17 mM MgSO₄, 22.6 mM NaHCO₃, 1.18 mM KH₂PO₄, 1.6 mM CaCl₂, 5.5 mM glucose, 50 mM sucrose) containing 4% bovine serum albumin. The 10 ml collected blood was added to the perfusate and subsequently mixed with the physiological salt solution as a perfusate for the isolated lungs. The roller pump (Minipuls 2; Gilson Medical Electronic, Middleton, WI, United States) was maintained at a flow rate of 8–10 ml/min. In situ isolated rat lungs were placed on an electronic scale to monitor real-time changes in lung weight. Left atrial pressure, which indicates pulmonary venous pressure (PVP), and the pulmonary artery pressure (PAP) were constantly recorded through the side arm of the cannula using pressure transducers (Gould Instruments, Cleveland, OH, United States).