A novel mechanism on disposing of effete enterocytes

1. 豚鼠小肠上皮细胞是细胞体的主要组成部分，被固有层巨噬细胞吞噬。然而，凋亡事件发生后，顶端细胞质仍留在上皮内。目前的研究表明，皮肤样的顶端细胞质通过连接复合物与邻近的肠细胞连接，仍然保持着上皮屏障。具有刷状边缘的顶端细胞质由于相邻细胞的闭合而凸出到管腔内，相邻细胞接触时又被挤压到管腔内。在此过程中，上皮未见孔洞。此后，肠腔内可见大量具有刷状边界的细胞质碎片。在大鼠肠管腔中，有大量凋亡的带核肠细胞细胞体，提示整个细胞体脱落进入肠管。在猴和马身上发现了豚鼠型的代谢机制，而在小鼠身上发现了大鼠型的代谢机制。人类基本上属于后一种。肠细胞的细胞死亡可能不是单纯的程序性细胞死亡，而容易受到外界因素的诱导。在豚鼠中上皮内淋巴细胞参与诱导细胞凋亡，而在大鼠固有层中巨噬细胞参与该机制。

1. Effete epithelial cells in the small intestine of the guinea pig, major parts of cell bodies, are phagocytosed by lamina propria macrophages. However, the apical cytoplasm remain within the epithe lium after the apoptotic event. The present study demonstrated that the skin-like apical cytoplasm is connected with adjacent enterocytes by junctional complexes, still keeping the epithelial barrier.2. The apical cytoplasm with the brush border is protruded into the luminal space due to closing of adjacent cells, and pinched off into the lumen when the adjacent cells contacted. During the process, no holes of the epithelium were recognizable. Thereafter, there were numerous cytoplasmic fragments with the brush border in the lumen of intestine.3. In the rat, the intestinal lumen contained numerous cell bodies of apoptotic enterocytes with nuclei, suggesting exfoliation of whole cell bodies into the lumen.4. The guines pig-type mechanism on disposing of effete epithelial cells was recognized in the monkey and horse, while the rat-type mechanism was shared by the mouse. Humans were basically classified into the latter type.5. Cell death of enterocytes may not be soley programd cell death, but easily induced by external factors. Intraepithelial lymphocytes are involved in the induction of apoptosis in the guinea pig, while in the rat lamina propria macrophages participate in this mechanism.