Effects of hydrogen peroxide on the guinea-pig tracheobronchial mucosa in vivo

Lumenal entry of plasma (mucosal exudation) is a key feature of airway infl ammation. In airways challenged with histamine-type mediators and allergen the mucosal exudation response occurs without causing epithelial derangemen t and without increased airway absorption. In contrast, reactive oxygen met abolites may cause mucosal damage. In this study, involving guinea-pig airw ays, we have examined effects of H2O2 On airway exudation and absorption in vivo. Vehicle or H2O2 (0.1 and 0.5 M) was superfused onto the tracheobronc hial mucosal surface through an oro-tracheal catheter. I-125-albumin, given intravenously, was determined in tracheobronchial tissue and in lavage flu ids 10 min after challenge as an index of mucosal exudation of plasma. The tracheobronchial mucosa was also examined by scanning electron microscopy. in separate animals, Tc-99m-DTPA was superfused 20 min after vehicle or H2O 2 (0.1 and 0.5 M) had been given. A gamma camera determined the disappearan ce rate of 99mTc-DTPA from the airways as an index of airway absorption. Th e high dose of H2O2 (0.5 M) produced epithelial damage, increased the absor ption of (TC)-T-99m-DTPA (P < 0.001), and increased the exudation of plasma (P < 0.001). Notably, it appeared that all extravasated plasma had entered the airway lumen within 10 min. These data demonstrate that H2O2 differs f rom exudative autacoids such as histamine by causing both epithelial damage and plasma exudation responses. These data also agree with the view that t he epithelial lining determines the rate of absorption and is responsible f or the valve-like function that allows lumenal entry of extravasated bulk p lasma without any increased inward perviousness.