Fate of inhaled nitrogen dioxide in isolated perfused rat lung.

The fate of inhaled NO2 was studied with isolated perfused rat lungs. The isolated lungs were exposed to 5 ppm NO2 for 90 min at a ventilation rate of 34 ml/min. The NO2 exposure had no adverse effects on the lungs as judged from their weights, glucose uptake, or lactate production compared to control lungs. Isolated lungs absorbed 36% of ventilated NO2, which was detected in perfusate and lung tissue as NO2- but not NO3-. The NO2- concentration in perfusate increased linearly with time, and after 90 min of ventilation with NO2 and perfusion with erythrocyte-free medium the NO2- accumulation was 6.36 +/- 0.39 micrograms. If perfusate contained 10% erythrocytes, the ventilated NO2 product was mostly NO3- in perfusate but NO2- in lung tissue. Protein solutions absorbed NO2 more effectively than simple salt solutions, but they all yielded mainly NO2- unless erythrocytes were present, when the product was mostly NO3-. The results indicate that absorbed NO2 in the lung is converted predominantly to NO2-, but after its diffusion into the vascular space it is oxidized to NO3- by interactions with erythrocytes.