Rao G H, Peller J D, White J G
Department of Laboratory Medicine, University of Minnesota Medical School, Minneapolis 55455, USA.
Thromb Res. 1997 Jan 1;85(1):23-31. doi: 10.1016/s0049-3848(96)00218-6.
The influence of ionized calcium on the down-regulation of GPIb/IX receptors on human platelets was evaluated by flow cytometry using monoclonal antibodies. Addition of EDTA alone to a washed platelet suspension did not cause decreased monoclonal antibody binding to the cells. However, introduction of thrombin to the washed platelets containing EDTA resulted in a marked decrease in binding of monoclonal antibodies to the GPIb/IX receptors. If calcium at 1-3 mmol/L was added to buffered platelets instead of EDTA before thrombin, down-regulation was prevented or significantly reduced. Restoring calcium to EDTA platelets after the thrombin-stimulated down-regulation had been in progress for 1-3 minutes caused reversal of decreased antibody binding by GPIb/IX to near resting levels. Results demonstrate that extracellular calcium is a major factor regulating thrombin-induced down-regulation.
通过使用单克隆抗体的流式细胞术评估了离子钙对人血小板上糖蛋白Ib/IX（GPIb/IX）受体下调的影响。仅向洗涤后的血小板悬液中添加乙二胺四乙酸（EDTA）不会导致单克隆抗体与细胞的结合减少。然而，将凝血酶引入含有EDTA的洗涤血小板中会导致单克隆抗体与GPIb/IX受体的结合显著减少。如果在添加凝血酶之前，向缓冲的血小板中添加1-3毫摩尔/升的钙而非EDTA，则可防止或显著减少下调。在凝血酶刺激的下调过程进行1-3分钟后，向含有EDTA的血小板中恢复钙会使GPIb/IX抗体结合减少逆转至接近静息水平。结果表明，细胞外钙是调节凝血酶诱导的下调的主要因素。
