Whur P, Koppel H, Urquhart C M, Williams D C
J Cell Sci. 1977 Apr;24:265-73. doi: 10.1242/jcs.24.1.265.
When BHK21 fibroblasts adhering to glass were incubated in trypsin they became spherical within a few minutes. They did not, however, respond simultaneously; the most trypsin-resistant cells in an unsynchronized population were of greater length, had more processes projecting from the cell body, and were more spread out than the most trypsin sensitive cells. In no instance did trypsin detach cells from their substrate, even when the incubation period was prolonged to 5 h in trypsin concentrations almost sufficient to cause cell lysis. Scanning electron-microscope observations showed that initially flat cells rounded up in trypsin to reveal persistent adhesion sites joined to the cell body by retraction fibres. Such cell could be dislodged only by agitation; when this occurred parts of the cell remained attached to the substrate in the form of small spheres and fibres; these were remnants of the retraction fibres and adhesion sites. We propose that the adhesion sites are not susceptible to proteolytic degradation, presumably because of steric hindrance, and that this causes detachment to be dependent upon mechanical dislocation. We suggest that some of the descriptions of substrate-associated 'cell exudates' in the literature may refer to these cell remnants on the substrate which consist of membrane-bound fragments of cytoplasm rather than secreted products.
当贴附在玻璃上的BHK21成纤维细胞在胰蛋白酶中孵育时，它们在几分钟内就会变成球形。然而，它们并非同时做出反应；在一个未同步化的细胞群体中，对胰蛋白酶最具抗性的细胞更长，从细胞体伸出的突起更多，并且比最敏感的细胞铺展得更开。即使将孵育时间延长至5小时，使用几乎足以导致细胞裂解的胰蛋白酶浓度，胰蛋白酶也从未使细胞从其底物上脱离。扫描电子显微镜观察表明，最初扁平的细胞在胰蛋白酶中变圆，露出通过收缩纤维与细胞体相连的持续附着位点。这样的细胞只有通过搅动才能被去除；当发生这种情况时，细胞的部分仍以小球和纤维的形式附着在底物上；这些是收缩纤维和附着位点的残余物。我们提出，附着位点不易受到蛋白水解降解的影响，大概是由于空间位阻，这使得脱离依赖于机械脱位。我们认为，文献中一些关于与底物相关的“细胞渗出物”的描述可能指的是底物上的这些细胞残余物，它们由细胞质的膜结合片段组成，而不是分泌产物。
