Effects of low-dose hydrogen peroxide in the isolated perfused rat lung

Isolated perfused rat lungs (IPRL) were used to determine if treatment with hydrogen peroxide would result in measurable changes in exhaled ethane during the early stages of capillary leak. Pulmonary capillary filtration coefficient, pulmonary vascular resistance, and dynamic pulmonary compliance were measured at two time points in an IPRL. Additionally, exhaled ethane was determined before and after the addition of 0.25 mM H₂O₂ to the perfusate in a second group of lungs. Lung wet/dry weight ratios were measured at the termination of the experiments. The ethane in the exhaled alveolar gas from IPRLs ventilated with 5%CO₂/20%O₂/balance N₂ was quantitated using gas chromatography before and after the addition of 0.25 mM H₂O₂ to Krebs Ringer's 5% albumin perfusate. H₂O₂ (0.25 mM) caused a small but significant increase in capillary filtration coefficient from 0.0122 (±0.0008) to 0.0173 (±0.0013) mL/min/cm H₂O/g dry lung weight (p <.05). Wet/dry lung weight ratios were increased in the H₂O₂-treated lungs (6.0654 ± 0.1024 versus 5.4149 ± 0.1143; p <.05). Exhaled ethane did not increase over the period of time hydrogen peroxide was present in the perfusate. In other experiments in closed-chested rats, 0.25 mM peroxide did not cause increased exhaled ethane, whereas 1 mM H₂O₂ did. This latter increase in ethane was not noted in similarly perfused open-chested rats. These data indicate that small amounts of H₂O₂ may increase pulmonary capillary permeability without affecting exhaled ethane measurements.