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.