Pulmonary responses to nutritional restriction and hyperoxia in premature rabbits.

OBJECTIVES To analyze the effects of nutritional restriction and hyperoxia on lung weight and pulmonary morphometry in premature rabbits during the first 11 days of life. METHODS New Zealand White rabbits were delivered by C-section at 28 days' gestational age and randomized into four groups: control diet and room air, control diet and hyperoxia (> or = 95% O2), nutritional restriction and room air and nutritional restriction and hyperoxia (> or = 95% O2). Nutritional restriction was achieved by reducing all nutrients by 30% in comparison with the control diet. Lung tissue slides were stained with hematoxylin-eosin, modified resorcin-orcein and picrosirius, before morphometric analysis was performed. RESULTS From the fourth day onwards, less weight was gained by the nutritional restriction and hyperoxia group (p < 0.001), and from the sixth day on, by the nutritional restriction and room air group (p < 0.001), in comparison with their respective control groups. Nutritional restriction decreased alveoli number (p < 0.001) and collagen deposition (p < 0.001). Hyperoxia was responsible for reductions in number of alveoli (p < 0.001) and collagen deposition (p < 0.001), in addition to higher mean linear intercept values (p < 0.05) and thickening of alveolar septa (p < 0.001). When nutritional restriction was associated with hyperoxia, the reductions in number of alveoli (p < 0.001) and of collagen deposition (p < 0.001) intensified. CONCLUSIONS Nutritional restriction intensified the changes of pulmonary architecture findings caused by hyperoxia, in particular through alterations to alveolarization and collagen deposition.