The effects of beta-aminopropionitrile on the growing rat lung.

beta-Aminopropionitrile (beta APN), 500 ng/g body weight was injected intraperitoneally into male rats every 2 days between 2 and 28 days after birth. The lungs were examined structurally and functionally and compared with the lungs of control animals given injections of saline and 28-day-old normal male rats which were not given injections. Lungs volumes, both distended with air at 30 cm H2O and with formalin at 25 cm H2O, were increased in beta APN-treated animals. The architecture of the lung was altered so that there was a large increase in the "core," or air internal to the alveoli of the walls of alveolar ducts and sacs. Animals given injections of beta APN had 40--56% fewer alveoli than those given saline injections and normal animals. Experimental animals had larger alveoli. The lungs or beta APN- treated animals were hypercompliant, and their pressure-volume curves were shifted upward and to the left. There were morphologic changes in collagen and elastic tissue, which were more apparent in the elastic tissue. Since beta APN interferes with the synthesis of elastin and collagen, it appears that alterations in the collagen--elastin network reduces alveolar multiplication in the postnatal period. Control animals given saline had abnormal lungs when compared with normal animals. Their alveoli were larger, and they had fewer alveoli per unit volume. Thus the lung may be sensitive to relatively minor insults in the postnatal period.