Studies on Oxygen Toxicity in the Lungs.

Work on two animal species has shown that during the first day of exposure to high concentrations of oxygen O2, the normal rate of cell division in the lung is decreased. In animals that survive the initial exposure to O2 or in those exposed to a lower concentration, cell division resumes after about five days. In animals exposed to O2, it has been noted that they eat less and lose weight. Air-breathing mice deprived of food had weight loss and depression in DNA synthesis similar to that observed in mice exposed to 95 percent O2. These results indicate that indirect factors are associated with the depression of DNA synthesis observed in mice exposed to high O2. Lack of food or 40 percent O2 did not inhibit type 2 division associated with repair of ozone damaged alveolar epithelium. Oxygen concentrations of 61 percent or higher did inhibit reparative cell division in ozone damaged alveoli of mice.