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 (L_ma). 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 L_ma (62.7 μm in C3 and 58.5 μm in B6) of 3-day-old mice. With increasing age (8 days), there was a progressive decrease in the L _ma of both strains, with the magnitude of the decrease in B6 L _ma 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.