The effect of beta-aminopropionitrile on lung development in the rat.

beta-Aminopropionitrile (beta APN) was administered intraperitoneally to rats on postnatal days 1, 3, and 5. Body weight, lung volume, lung weight, number of alveoli per unit area and volume, total number of alveoli in the lung, and the total length of elastic fibers in the lung decreased, and the average alveolar volume increased in comparison with control animals similarly treated with saline. From Day 2 of age to Day 6 the total length of elastic fibers increased in control lungs but remained almost the same following beta APN treatment. Ultrastructurally, both the quality and quantity of elastin in lung alveolar wall were affected. beta APN also inhibited the synthesis of deoxyribonucleic acid in interstitial, endothelial, and Type II epithelial cells of the lung alveolar wall. The diminished number of alveoli gives support to the hypothesis that the elastin-collagen network may play a key role in postnatal alveolar multiplication.