Tschanz Stefan A, Salm Lilian A, Roth-Kleiner Matthias, Barré Sebastien F, Burri Peter H, Schittny Johannes C
Institute of Anatomy, University of Bern, Bern, Switzerland; and.
Clinic of Neonatology, University Hospital and University of Lausanne, Lausanne, Switzerland.
J Appl Physiol (1985). 2014 Jul 1;117(1):89-95. doi: 10.1152/japplphysiol.01355.2013. Epub 2014 Apr 24.
Roughly 90% of the gas-exchange surface is formed by alveolarization of the lungs. To the best of our knowledge, the formation of new alveoli has been followed in rats only by means of morphological description or interpretation of semiquantitative data until now. Therefore, we estimated the number of alveoli in rat lungs between postnatal days 4 and 60 by unambiguously counting the alveolar openings. We observed a bulk formation of new alveoli between days 4 and 21 (17.4 times increase from 0.8 to 14.3 millions) and a second phase of continued alveolarization between days 21 and 60 (1.3 times increase to 19.3 million). The (number weighted) mean volume of the alveoli decreases during the phase of bulk alveolarization from ∼593,000 μm(3) at day 4 to ∼141,000 μm(3) at day 21, but increases again to ∼298,000 μm(3) at day 60. We conclude that the "bulk alveolarization" correlates with the mechanism of classical alveolarization (alveolarization before the microvascular maturation is completed) and that the "continued alveolarization" follows three proposed mechanisms of late alveolarization (alveolarization after microvascular maturation). The biphasic pattern is more evident for the increase in alveolar number than for the formation of new alveolar septa (estimated as the length of the free septal edge). Furthermore, a striking negative correlation between the estimated alveolar size and published data on retention of nanoparticles was detected.
大约90%的气体交换表面是由肺的肺泡化形成的。据我们所知，到目前为止，仅通过形态学描述或半定量数据的解释来追踪大鼠新肺泡的形成。因此，我们通过明确计数肺泡开口来估计出生后第4天至60天大鼠肺中的肺泡数量。我们观察到在第4天至21天之间有大量新肺泡形成（从0.8百万增加到14.3百万，增加了17.4倍），以及在第21天至60天之间有第二阶段的持续肺泡化（增加到1930万，增加了1.3倍）。在大量肺泡化阶段，肺泡的（数量加权）平均体积从第4天的约593,000μm³降至第21天的约141,000μm³，但在第60天又再次增加到约298,000μm³。我们得出结论，“大量肺泡化”与经典肺泡化机制（在微血管成熟完成之前的肺泡化）相关，而“持续肺泡化”遵循三种提出的晚期肺泡化机制（微血管成熟后的肺泡化）。肺泡数量的增加比新肺泡隔形成（估计为游离隔边缘的长度）的双相模式更明显。此外，检测到估计的肺泡大小与已发表的纳米颗粒滞留数据之间存在显著的负相关。
