Proliferation of lung cells in chronically hypoxic rats

Summary Alveolar hypoxia produces pulmonary hypertension and morphological alterations in the pulmonary vessels, such as media hypertrophy and hyperplasy of pulmonary arteries as well as development of smooth muscle cells in the wall of small precapillary arteries. Chronic hypoxia induces an increase in the DNA-synthesis rate of lung tissue and this study confirms this previously reported result using in vivo incorporation of ³H-thymidine. Autoradiographic investigations demonstrate an increase in the ³H-thymidine labelling index of cells in the bronchial epithelial lining, of lung parenchyma cells, and of smooth muscle cells in the media of pulmonary arteries after 9 days of exposure to a simulated altitude of 4250 m (Pb = 440 Torr).In contrast, in control tissue from rat liver and kidney chronic hypoxia inhibits the proliferation of sinusoid endothelial cells and Kupffer cells and also the proliferation of renal tubulus epithelial cells. Our results indicate that (1) chronic hypoxia stimulates proliferation of various cell types in the rat lung; (2) cells of the bronchial epithelial lining respond to chronic hypoxia with very high proliferation rates; and (3) the formation of new media smooth muscle cells may contribute to the adaptation process of the pulmonary arteries of chronically hypoxic rats.These results can contribute to the understanding of pulmonary hypertension, an often severe concomitant reaction of chronic lung diseases.