Effects of elevated P02 upon tracheal explants.

Time-dependent effects of elevated PO2 upon hamster tracheal rings in culture were examined. Ciliary activity of rings in 0.20 and 0.40 O2 remained stable for 144 h. Ciliary activity decreased 25% following 120 h exposure to 0.60 O2 and 50% within 72 h exposure to 0.95 O2. Ciliostasis occurred by 144 h at 0.95 O2. [3H]Leucine uptake progressively decreased during 24 to 144 h exposure to 0.40, 0.60, and 0.95 O2 when compared to 0.20 O2. Tracheal explants incubated for 6 days under 0.20 and 0.40 O2 had intact epithelial surface with abundant cilia, and no mucus present (scanning electron microscopy). Explants incubated under 0.60 O2 contained mucus globules by 3 days. Incubation in 0.95 O2 resulted in mucus globules within 3 days and epithelial sloughing, loss of cilia, and increased mucus globules within 6 days. Time and O2 dependent increases in nuclear atypia, leukocytic infiltration into submucosal area, and focal flattening of pseudostratified ciliated epithelium were observed (light microscopy). These changes progressed following 6 days' exposure to 0.95 O2 to complete loss of normal epithelium, with broken-up, epithelial cells along the tracheal lumen.