Holevinsky K O, Nelson D J
Department of Pharmacological and Physiological Sciences, The University of Chicago, Chicago, Illinois 60637, USA.
Biophys J. 1998 Nov;75(5):2577-86. doi: 10.1016/S0006-3495(98)77703-3.
We report the use of capacitance measurements to monitor particle uptake after cellular exposure to phagocytic stimuli. In these studies, human monocyte-derived macrophages (HMDMs) and cells from the murine macrophage-like cell line J774.1 were exposed to immune complexes or sized latex particles (0.8 or 3.2 micron in diameter). An average decrease in cell capacitance of 8 pF was seen after exposure of the cells to immune complexes. Cells in which particle uptake was inhibited by cytochalasin B treatment before exposure to immune complexes showed an average increase of 0.5 pF. The decrease in membrane capacitance after exposure of cells to particulate stimuli was absent with the soluble stimulus, platelet-activating factor, further confirming that decreases in membrane capacitance were due to particle uptake. Exposure of cells to sized latex particles resulted in a graded, stepwise decrease in membrane capacitance. The average step size for 0.8-micron particles was 250 fF, and the average step change for the larger 3.2-micron particles was 480 fF, as calculated from Gaussian fits to the step size amplitude histograms. The predicted step size for the individual particles based upon the minimum amount of membrane required to enclose a particle and a specific capacitance of 10 fF/micron2 was 20 and 320 fF, respectively. The step size for the smaller particles deviates significantly from the predicted size distribution, indicating either a possible lower limit to the size of the phagocytic vacuole or multiple particles taken up within a single phagosome. Dynamic interaction between phagocytosis and exocytosis was observed in a number of cells as a biphasic response consisting of an initial rapid increase in capacitance, consistent with cellular exocytosis, followed by stepwise decreases in capacitance.
我们报告了利用电容测量来监测细胞暴露于吞噬刺激后颗粒摄取情况。在这些研究中，将人单核细胞衍生的巨噬细胞（HMDMs）和小鼠巨噬细胞样细胞系J774.1的细胞暴露于免疫复合物或大小分级的乳胶颗粒（直径0.8或3.2微米）。细胞暴露于免疫复合物后，细胞电容平均下降8 pF。在暴露于免疫复合物之前用细胞松弛素B处理抑制颗粒摄取的细胞，其电容平均增加0.5 pF。可溶性刺激物血小板活化因子不会使细胞暴露于颗粒刺激后膜电容下降，这进一步证实膜电容下降是由于颗粒摄取所致。细胞暴露于大小分级的乳胶颗粒会导致膜电容呈分级、逐步下降。根据对步长幅度直方图的高斯拟合计算，0.8微米颗粒的平均步长为250 fF，较大的3.2微米颗粒的平均步长变化为480 fF。基于包裹一个颗粒所需的最小膜量和10 fF/微米²的比电容，单个颗粒的预测步长分别为20和320 fF。较小颗粒的步长明显偏离预测的大小分布，这表明吞噬泡大小可能存在下限，或者单个吞噬体内摄取了多个颗粒。在许多细胞中观察到吞噬作用和胞吐作用之间的动态相互作用，表现为双相反应，包括电容最初的快速增加，这与细胞胞吐作用一致，随后电容逐步下降。
