Fig. 1

H₂O₂ effects on junctions of differentiated NHBE cells. NHBE cultures were mounted in Ussing chambers and exposed to H₂O₂ (panels a, c-d). Panel a. Acute exposure to apical 1 mM H₂O₂ elicits a transient increase in Isc (upward arrow head) and prolonged exposure induces a decrease in membrane resistance (downward arrow head). Note the size of the current after voltage pulses prior to the addition of H₂O₂ compared to the much larger current from pulses 40 min after exposure. Larger currents signify lower membrane resistances. For all experiments, transepithelial membrane resistances were measured 40–60 min after H₂O₂ exposure. Panel b. Prolonged exposure to apical 1 mM H₂O₂ elicits a concomitant increase in paracellular permeability to mannitol (circles: no treatment, squares: H₂O₂ treated, mean ± s.e.m., n = 7 cultures from 5 lung donors). Panel c. The observed decrease in membrane resistance after 40 min is dependent on the H₂O₂ concentration (mean ± s.e.m., n = 8 cultures from 4 donors). Panel d. The H₂O₂-induced change in resistance is dependent on the length of H₂O₂ exposure. Removing H₂O₂ from the perfusate within 5 min of exposure prevents the large change in resistance measured after 40 min