Ikehata Mika, Yumoto Ryoko, Nakamura Kosuke, Nagai Junya, Takano Mikihisa
Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8553, Japan.
Pharm Res. 2008 Apr;25(4):913-22. doi: 10.1007/s11095-007-9426-x. Epub 2007 Sep 11.
To elucidate and compare the activity and mechanism of albumin uptake in primary cultured alveolar type II and type I-like epithelial cells.
Type II epithelial cells isolated from rat lungs were cultured for 2 days at 5 x 10(6) cells/35-mm dish or for 6 days at 2 x 10(6) cells/35-mm dish. The mRNA expression of marker genes and FITC-albumin uptake were examined.
The cells cultured for 2 days exhibited cuboidal type II epithelial morphology with lamellar bodies inside the cells, while the cells cultured for 6 days exhibited squamous type I epithelial morphology. These morphological characteristics were consistent with the changes in mRNA expression pattern of marker genes. FITC-albumin uptake in both cells was temperature-dependent and was inhibited by metabolic inhibitors and bafilomycin A1. The rate of uptake was much higher in type II cells than type I-like cells. In both cells, FITC-albumin uptake was inhibited by clathrin mediated-endocytosis inhibitors, but not by caveolae mediated-endocytosis inhibitors.
These findings indicate that albumin in alveolar lining fluid is internalized into type II and type I epithelial cells via clathrin-mediated endocytosis, and the rate of albumin uptake is higher in type II cells than type I cells.
阐明并比较原代培养的肺泡Ⅱ型上皮细胞和Ⅰ型样上皮细胞摄取白蛋白的活性及机制。
从大鼠肺中分离出的Ⅱ型上皮细胞，以5×10⁶个细胞/35毫米培养皿培养2天，或以2×10⁶个细胞/35毫米培养皿培养6天。检测标记基因的mRNA表达及异硫氰酸荧光素（FITC）标记白蛋白的摄取情况。
培养2天的细胞呈现立方形Ⅱ型上皮形态，细胞内有板层小体，而培养6天的细胞呈现扁平状Ⅰ型上皮形态。这些形态学特征与标记基因mRNA表达模式的变化一致。两种细胞摄取FITC标记白蛋白均呈温度依赖性，且受代谢抑制剂和巴弗洛霉素A1抑制。Ⅱ型细胞的摄取速率远高于Ⅰ型样细胞。在两种细胞中，FITC标记白蛋白的摄取均受网格蛋白介导的内吞作用抑制剂抑制，但不受小窝蛋白介导的内吞作用抑制剂抑制。
这些发现表明，肺泡衬液中的白蛋白通过网格蛋白介导的内吞作用进入Ⅱ型和Ⅰ型上皮细胞，且Ⅱ型细胞摄取白蛋白的速率高于Ⅰ型细胞。
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