LUNG CYTOKINETICS AFTER EXPOSURE TO HYPOBARIA AND OR HYPOXIA AND UNDERNUTRITION IN GROWING RATS/

Lung cellular dynamics were examined in growing rats from 4 to 7 wk of age after exposure to 1) room air (general controls), 2) hypobaric no rmoxia, 3) normobaric hypoxia, 4) hypobaric hypoxia, and 5) room air a nd restricted food intake (weight-matched controls). Tritiated thymidi ne ([H-3]TdR) incorporation diminished in weight-matched controls. In both hypoxic groups, maximum [H-3]TdR incorporation occurred on day 3 in all cells of peripheral alveoli, capillary endothelium of central a lveoli, airway walls and epithelium, and arterial wall and endothelium , but maximum [H-3]TdR labeling of interstitial and unidentifiable cel ls of central alveoli occurred on day 5. The percent labeling with [H- 3]TdR was higher in cells of peripheral alveolar walls than in cells o f central alveolar walls. Labeling of the interstitium was higher in h ypobaric hypoxic than normobaric hypoxic rats. In hypobaric normoxia, DNA synthetic activity increased in alveolar wall cells, except for ca pillary endothelium. In hypobaric hypoxia, DNA synthesis occurred prim arily because of low O-2, but low pressure may also affect cytokinetic s. [H-3]TdR incorporation is greater and earlier in the alveoli of the peripheral part of the lung than central alveoli, and the cellular re sponse of the various cells types is not synchronous.