Pitkänen O M, O'Brodovich H M
Hospital for Children and Adolescents, University of Helsinki, Finland.
Ann Med. 1998 Apr;30(2):134-42. doi: 10.3109/07853899808999396.
Active ion transport plays a critical role in the liquid movement across the fetal and perinatal lung epithelium. The fetal lung liquid production is coupled with active secretion of Cl- into the luminal space. The potential for fluid absorbing mechanisms related to active Na+ transport from the apical to the basolateral side of the epithelium appears near the end of gestation. At birth there is a dramatic change of environment with commencement of air-breathing, sudden increase in oxygen partial pressure (PO2) and profound changes in the pulmonary circulation. A concurrent switch from fluid secretion to maintenance of low amounts of alveolar fluid is another major physiological adjustment taking place in the perinatal distal lung epithelium. The fluid-absorbing mechanism is a result of a well-synchronized co-operation between the basolateral membrane Na-K-ATPase and the apical membrane Na+ channels and it promotes salt and water movement from the airspace. Inability of the fetal lung epithelium to switch from fluid secretion to Na+ transport-dependent absorption seems to be an important factor adversely contributing to the respiratory distress of the newborn premature infant.
主动离子转运在胎儿及围产期肺上皮液体转运过程中起着关键作用。胎儿肺液的产生与氯离子向管腔空间的主动分泌相关联。与上皮细胞从顶端向基底外侧主动转运钠离子相关的液体吸收机制在妊娠末期开始出现。出生时，随着呼吸的开始、氧分压（PO2）的突然升高以及肺循环的深刻变化，环境发生了巨大改变。围产期远端肺上皮同时发生的从液体分泌到维持少量肺泡液的转变是另一项主要的生理调节。液体吸收机制是基底外侧膜钠钾ATP酶与顶端膜钠离子通道之间良好同步协作的结果，它促进盐和水从气腔中转运。胎儿肺上皮无法从液体分泌转换为依赖钠离子转运的吸收似乎是导致早产新生儿呼吸窘迫的一个重要不利因素。
