EFFECT OF HYPOXIA AND HYPEROXIA ON POSTPNEUMONECTOMY COMPENSATORY LUNG GROWTH

To study the effect of chronic hyperoxia and hypoxia on pneumonectomy- induced compensatory lung growth, 4-week-old male rats were randomly d ivided into 4 groups: pneumonectomy controls, pneumonectomy hyperoxic group (fraction of ambient oxygen {FO2} 0.35), pneumonectomy hypoxic g roup (FO2 0.14), and unoperated controls. After 2 weeks, somatic growt h of pneumonectomy hypoxic rats was diminished. Compared to unoperated controls, lung weight increased in all pneumonectomy groups but lung volume increased only in pneumonectomy control and pneumonectomy hypox ic rats. Alveolar surface area also increased in pneumonectomy control and pneumonectomy hypoxic animals. Lung weight, volume, and alveolar surface area in pneumonectomy hypoxic rats were also significantly hig her than in pneumonectomy hyperoxic rats. When lung weight, volume, al veolar surface area, and total number of alveoli were normalized for b ody weight, the values were significantly higher in pneumonectomized h ypoxic rats than in the pneumonectomy control and pneumonectomy hypero xic groups. Maximal increase in volume occurred in the post-caval and upper lobes in all pneumouectomized groups. Compared to unoperated rat s, mean linear intercept also increased in the post-caval lobe in all pneumonectomized groups. The results suggest that 2 weeks after left p neumonectomy, compensatory lung response is incomplete. Chronic hypoxi a enhances, whereas hyperoxia inhibits compensatory lung growth. The p ost-caval and upper lobes respond more and the lower lobe responds les s following left pneumonectomy in both hypoxia and hyperoxia.