Ingbar D H, Weeks C B, Gilmore-Hebert M, Jacobsen E, Duvick S, Dowin R, Savik S K, Jamieson J D
Department of Medicine, University of Minnesota, Minneapolis 55455, USA.
Am J Physiol. 1996 Apr;270(4 Pt 1):L619-29. doi: 10.1152/ajplung.1996.270.4.L619.
Late in gestation lung epithelium changes from net chloride and fluid secretion to sodium and fluid absorption. Fluid resorption is required for postnatal gas exchange and occurs by combined action of epithelial sodium channels and Na, K-ATPase. We hypothesized that alveolar epithelial Na, K-ATPase increases perinatally. Immunofluorescence (IF) and immunoelectron microscopy (IEM) with a monoclonal anti-alpha subunit antibody demonstrated that Na, K-ATPase was present on the basolateral surfaces of columnar epithelial cells at fetal day (FD) 17 and on type II cells throughout development. However, type I epithelial cells did not have detectable Na,K-ATPase. The steady-state levels of both the alpha 1 isoform and the beta-subunit mRNAs were maximal at FD20-neonatal day (ND) 1, with consistent increases from FD17 level. Na, K-ATPase alpha-subunit protein also increased from FD17 to FD20-22 and then decreased in the early postnatal period. The ouabain-inhibitable sodium pump activity per milligram membrane protein increased 2.6-fold from FD17 to FD22-ND1 (P < 0.05). The quantities of sodium pump mRNA, antigenic protein, and enzyme activity increase in late gestation in accord with a proposed role for Na, K-ATPase in resorption of alveolar sodium and fluid in preparation for birth.
在妊娠后期，肺上皮细胞从净氯化物和液体分泌转变为钠和液体吸收。产后气体交换需要液体重吸收，这是由上皮钠通道和钠钾ATP酶的共同作用实现的。我们假设肺泡上皮钠钾ATP酶在围产期增加。用单克隆抗α亚基抗体进行免疫荧光（IF）和免疫电子显微镜（IEM）检测表明，在胎儿第17天，钠钾ATP酶存在于柱状上皮细胞的基底外侧表面，并且在整个发育过程中II型细胞上也有。然而，I型上皮细胞未检测到钠钾ATP酶。α1同工型和β亚基mRNA的稳态水平在胎儿第20天至新生第1天达到最大值，相对于胎儿第17天的水平持续增加。钠钾ATP酶α亚基蛋白也从胎儿第17天增加到胎儿第20 - 22天，然后在出生后早期下降。每毫克膜蛋白的哇巴因抑制性钠泵活性从胎儿第17天到胎儿第22天至新生第1天增加了2.6倍（P < 0.05）。钠泵mRNA、抗原性蛋白和酶活性的量在妊娠后期增加，这与钠钾ATP酶在为出生做准备时对肺泡钠和液体重吸收中的作用一致。
