Comparison of postnatal lung growth and development between C3H/HeJ and C57BL/6J mice.

Previous work by our group has demonstrated substantial differences in lung volume and morphometric parameters between inbred mice. Specifically, adult C3H/HeJ (C3) have a 50% larger lung volume and 30% greater mean linear intercept than C57BL/6J (B6) mice. Although much of lung development occurs postnatally in rodents, it is uncertain at what age the differences between these strains become manifest. In this study, we performed quasi-static pressure-volume curves and morphometric analysis on neonatal mice. Lungs from anesthetized mice were degassed in vivo using absorption of 100% O2. Pressure-volume curves were then recorded in situ. The lungs were then fixed by instillation of Zenker's solution at a constant transpulmonary pressure. The left lung from each animal was used for morphometric determination of mean air space chord length (Lma). We found that the lung volume of C3 mice was substantially greater than that of B6 mice at all ages. In contrast, there was no difference in Lma (62.7 microm in C3 and 58.5 microm in B6) of 3-day-old mice. With increasing age (8 days), there was a progressive decrease in the Lma of both strains, with the magnitude of the decrease in B6 Lma mice exceeding that of C3. C3 lung volume remained 50% larger. The combination of parenchymal architectural similarity with lung air volume differences and different rates of alveolar septation support the hypothesis that lung volume and alveolar dimensions are independently regulated.