Gutierrez J A, Gonzalez R F, Dobbs L G
Department of Pediatrics, University of California, San Francisco 94143-0106, USA.
Am J Physiol. 1998 Feb;274(2):L196-202. doi: 10.1152/ajplung.1998.274.2.L196.
The pulmonary alveolar epithelium is composed of two distinct types of cells, type I and type II cells, both of which are critical for normal lung function. On the basis of experiments of both nature and in vivo studies, it has been hypothesized that expression of the type I or type II phenotype is influenced by mechanical factors. We have investigated the effects of mechanical distension on the expression of specific markers for the type I and type II cell phenotypes in cultured alveolar type II cells. Rat alveolar type II cells were tonically mechanically distended in culture. Cells were analyzed for a marker for the type I phenotype (rTI40, an integral membrane protein specific for type I cells) and for markers for the type II phenotype [surfactant protein (SP) A, SP-B, and SP-C] as well as for glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Mechanical distension caused a 68 +/- 25% (n = 3) increase in mRNA content of rTI40 relative to undistended controls. In contrast, mechanical distension resulted in a decrease in mRNA content of SP-B to 35 +/- 19% (n = 3) and of SP-C to 20 +/- 6.7% (n = 3) of undistended controls. There was no effect on mRNA content of SP-A or GAPDH. The differences in mRNA content of SP-B and SP-C were found to be primarily due to changes at the transcriptional level by nuclear run-on assays. The effects on rTI40 appear to be due to posttranscriptional events. These data show that mechanical distension influences alveolar epithelial phenotypic expression in vitro, at least in part, at the transcriptional level.
肺泡上皮由两种不同类型的细胞，即I型和II型细胞组成，这两种细胞对于正常肺功能都至关重要。基于自然实验和体内研究，有人提出I型或II型表型的表达受机械因素影响。我们研究了机械扩张对培养的II型肺泡细胞中I型和II型细胞表型特异性标志物表达的影响。在培养中对大鼠II型肺泡细胞进行持续机械扩张。分析细胞中I型表型标志物（rTI40，一种I型细胞特异性整合膜蛋白）、II型表型标志物[表面活性蛋白（SP）A、SP-B和SP-C]以及甘油醛-3-磷酸脱氢酶（GAPDH）。机械扩张使rTI40的mRNA含量相对于未扩张对照增加了68±25%（n = 3）。相比之下，机械扩张导致SP-B的mRNA含量降至未扩张对照的35±19%（n = 3），SP-C的mRNA含量降至未扩张对照的20±6.7%（n = 3）。对SP-A或GAPDH的mRNA含量没有影响。通过核转录分析发现，SP-B和SP-C的mRNA含量差异主要是由于转录水平的变化。对rTI40的影响似乎是由于转录后事件。这些数据表明，机械扩张至少在一定程度上在转录水平影响体外肺泡上皮表型表达。
