Effects of hyperoxia on transtracheal chloramphenicol influx

Effects of exposure to high partial pressures of oxygen on transtracheal influx of chloramphenicol (Chlor) were examined using in vitro perfusion of the rat trachea. Net Chlor influx decreased with increasing duration of exposure to 100% O2 from control levels of 37.0 +/- 2.4 ng.min-1.trachea-1 to 30.0 +/- 1.0 ng.min-1.trachea-1 after 36 h of exposure to 100% O2 and was further depressed after 48 h of exposure to 100% O2 60 23.0 +/- 0.9 ng.min-1.trachea-1. Examination of the O2-exposed tracheas by light microscopy showed normal morphology. In contrast, net Chlor influx was not affected by exposure to 50% O2 for 48 h. In a separate group of rats recovery from the effects of hyperoxia was studied. Within 24 h after removal from the hyperoxic environment, net Chlor influx had returned to control levels. We conclude that high partial pressures of oxygen inhibit net Chlor influx in the rat trachea at a time when tracheal histology is normal. This inhibition is a function of the partial pressure of oxygen and the duration of exposure and it is reversible after removal from the hyperoxic environment.