Barker P M, Gatzy J T
Department of Pediatrics, School of Medicine, University of North Carolina at Chapel Hill 27599.
Am J Physiol. 1993 Nov;265(5 Pt 1):L512-7. doi: 10.1152/ajplung.1993.265.5.L512.
Throughout gestation, fetal lung is filled with liquid secreted by the pulmonary epithelium. Factors responsible for secretion and for induction of liquid absorption by postnatal lung are poorly understood. We studied effects of "fetal" (3% O2-8% CO2) and "postnatal" (21% O2-5% CO2) gas tensions and of low hormone concentrations [media with 10% charcoal-stripped fetal bovine serum (stFBS) or unstripped FBS] on water content and morphology of distal lung explanted from 14-, 20-, and 22-day fetal (term, 22 days) and 2-day neonatal rats and incubated in submersion culture. Water-to-dry weight ratios of freshly excised fetal whole lung at 20 (6.2) or 22 days (7.0) were greater than that of 2-day postnatal lung (4.7). Culture conditions did not affect water-to-dry weight ratio of cyst-forming 14-day explants (10.8) or acystic 2-day postnatal explants (2.4). Fetal gases and stFBS supported cyst formation in [and high water/dry weight (9.2, 12.6) of] 20- and 22-day explants. Cysts also formed in 20-day explants exposed to postnatal gases and stFBS (water/dry weight = 6.5). Other conditions resulted in minimal cyst formation by 20- and 22-day explants and in water/dry weight similar to that of freshly excised and drained distal lung from 22-day fetuses (2.1). Cysts were lined with cuboidal and thin epithelial cells. No cells were ciliated. We conclude that 1) secretion dominates liquid flow across epithelia of fetal rat lung until birth, 2) alveolar epithelium contributes to this secretion, and 3) liquid secretion by fetal distal lung late in gestation is regulated by gas composition.
在整个妊娠期，胎儿肺充满了由肺上皮分泌的液体。对于产后肺分泌和诱导液体吸收的相关因素，人们了解甚少。我们研究了“胎儿期”（3%氧气 - 8%二氧化碳）和“产后”（21%氧气 - 5%二氧化碳）气体张力以及低激素浓度[含10%活性炭处理的胎牛血清（stFBS）或未处理的FBS的培养基]对从14天、20天和22天胎龄（足月为22天）的胎儿以及2日龄新生大鼠取出的远端肺组织的含水量和形态的影响，这些组织在浸没培养中进行孵育。20天（6.2）或22天（7.0）的新鲜切除的胎儿全肺的水干重比大于产后2日龄肺（4.7）。培养条件不影响形成囊肿的14天组织块（10.8）或无囊肿的产后2日龄组织块（2.4）的水干重比。胎儿气体和stFBS支持20天和22天组织块形成囊肿[且水/干重较高（9.2，12.6）]。暴露于产后气体和stFBS的20天组织块也形成了囊肿（水/干重 = 6.5）。其他条件导致20天和22天组织块形成的囊肿极少，且水/干重与新鲜切除并沥干的22天胎儿远端肺相似（2.1）。囊肿内衬立方状和扁平上皮细胞。无纤毛细胞。我们得出结论：1）在出生前，分泌主导着液体通过胎鼠肺上皮的流动；2）肺泡上皮参与这种分泌；3）妊娠后期胎儿远端肺的液体分泌受气体成分调节。
