Materials and Methods

Animals Guaranteed timed-pregnant Fischer 344 rats were obtained from the National Cancer Institute (Frederick, MD) at day 14 of gestation. The animals were housed in a barrier facility and provided food and water ad libitum throughout the study. Rats were studied at days 15 through 21 of gestation, days 5, 8, 19, and 25 of postnatal life, and adulthood. Pulmonary tissue from three animals was examined at each point. These specimens were obtained from at least two different litters to permit examination of littermates at more than one time point and to control for developmental variation due to litter size.

In the lung injury studies, adult male Fischer 344 rats weighing approximately 200 g were used. Bleomycin sulfate (Blenoxane Bristol Labs, Syracuse, NY) was administered to the experimental animals at a dose of 0.75 U/IOO g body weight in 0.2 ml of sterile saline via intratracheal instillation as previously described (14). Control animals received no treatment or sterile saline only. Animals were sacrificed by sodium pentobarbital overdose at 14 days after treatment. All animal protocols had the approval of the University Institutional Animal Care and Use Committee (IACUC).