Dunsmore S E, Rannels D E
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033.
Am J Physiol. 1995 Feb;268(2 Pt 1):L336-46. doi: 10.1152/ajplung.1995.268.2.L336.
Rat type II pulmonary epithelial cells synthesize and assemble a multicomponent extracellular matrix (ECM) which can modulate cellular differentiation in primary culture. This study defines turnover of the type II cell matrix. Turnover kinetics were analyzed in two types of pulse-chase protocols based on loss of radioactive ECM components. To estimate turnover of previously synthesized ECM, type II cells were plated on extracted matrix that was radiolabeled 2, 3, or 6 days; alternatively, ECM was radiolabeled in pulse-chase experiments to measure turnover by the same cells that synthesized the matrix. Rapid initial rates of ECM turnover were evident in both cases. While overall matrix stability appeared to change with culture time, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed a similar spectrum of proteins in the ECM over the course of kinetic studies. The results reveal rapid turnover of ECM by type II cells and suggest that matrix stability may be regulated. These observations provide a basis for future investigations of the physiological significance of turnover of individual ECM components by the alveolar epithelium.
大鼠II型肺上皮细胞合成并组装一种多组分细胞外基质（ECM），该基质可在原代培养中调节细胞分化。本研究定义了II型细胞基质的更新情况。基于放射性ECM成分的损失，在两种脉冲追踪实验方案中分析了更新动力学。为了估计先前合成的ECM的更新情况，将II型细胞接种在分别于2天、3天或6天进行放射性标记的提取基质上；或者，在脉冲追踪实验中对ECM进行放射性标记，以测量合成该基质的相同细胞的更新情况。在这两种情况下，ECM更新的初始速率都很快。虽然总体基质稳定性似乎随培养时间而变化，但在动力学研究过程中，十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析显示ECM中的蛋白质谱相似。结果揭示了II型细胞对ECM的快速更新，并表明基质稳定性可能受到调节。这些观察结果为未来研究肺泡上皮细胞对单个ECM成分更新的生理意义提供了基础。
