The preterm rat: a model for studies of acute and chronic neonatal lung disease.

A preterm rat model has been developed for studies of acute and chronic neonatal lung disease. Premature delivery 24 h before the normal time of delivery is associated with immature pulmonary phospholipid and antioxidant enzyme profiles. The premature lung is more fragile and ruptures at a lower lung vol (172 +/- 8 microL) than the full-term fetal lung (259 +/- 14 microL). Only 7% of premature lungs will float in liquid, after inflation to 85% of the rupture vol, compared with 87% of term fetal lungs. This lung immaturity was reflected in a survival rate of only 6% by 36 h after delivery if the preterm pups were placed in air, which increased to 47% when they were placed in greater than 95% oxygen. Though greater than 95% oxygen enhanced survival of preterm pups during the 1st wk of life, these survivors had a 50% mortality during the 2nd wk of exposure to greater than 95% oxygen. The preterm pup will tolerate intraperitoneal injection of antioxidant enzymes entrapped in liposomes and has a better retention of these liposomes in the lung compared with the term pup. We conclude that the preterm rat is a suitable model for studies of acute and chronic neonatal lung disease.