Effects of high altitude exposure on the lungs of young rats

Abstract

Month-old male rats were exposed in a hypobaric chamber to a simulated altitude of 4200 m (Pb = 450 mm Hg). After 20–21 days, exposed animals had significantly greater lung volumes and alveolar surface areas than controls. Animals sacrificed after 7 days of exposure had lungs that were abnormally heavy relative to their volume; this increase in lung density was due to an increase in non-blood lung water, presumably as edema fluid. After 20–21 days, lung density and water content had returned essentially to normal. The volume of blood remaining in the lungs after removal from the animal was not influenced by high altitude exposure. The findings indicate that young rats exposed to high altitude undergo an initial period of mild pulmonary edema; during this period the rate of alveolar development is probably not increased above normal. With continued exposure, the edema subsides and alveolar proliferation occurs at a faster rate than in control animals. This results eventually in increased lung volumes and alveolar surface areas in high altitude animals, a change which probably has adaptive significance.