Effects of acute hyperoxic exposure on solute fluxes across the blood-gas barrier in rat lungs.

We investigated effects of acute hyperoxia on solute transport from air space to vascular space in isolated rat lungs. Air spaces were filled with Krebs-Ringer bicarbonate solution containing fluorescein isothiocyanate-labeled dextran (FD-20; mol wt 20,000) and either 22Na+ and [14C]sucrose, or D-[14C]glucose and L-[3H]glucose. Apparent permeability-surface area products for tracers over time (up to 120 min) were calculated for isolated perfused lungs from control rats (room air) and rats exposed to > 95% O2 for 48 or 60 h immediately postexposure. After O2 exposures, mean fluxes for [14C]sucrose and FD-20 were significantly higher than in room-air control lungs. However, amiloride-sensitive Na+ and active D-glucose fluxes were unchanged after hyperoxic exposure. Therefore, it is unlikely that decreases in net solute transport in this lung-injury model contributed to pulmonary edema resulting from O2 toxicity. Increased net solute transport shown to help resolve pulmonary edema after acute hyperoxic exposure must therefore begin during the recovery period. In summary, our data show increases in passive solute fluxes but no changes in active solute fluxes immediately after acute hyperoxic lung injury.