Release of azurophilic granule contents in fMLP-stimulated neutrophils requires two activation signals, one of which is a rise in cytosolic free Ca |
| |
Authors: | Hans W. M. Niessen Taco W. Kuijpers Dirk Roos Arthur J. Verhoeven |
| |
Affiliation: | Central Laboratory of the Netherlands Red Cross Blood Transfusion Service and Laboratory of Experimental and Clinical Immunology of the University of Amsterdam, Amsterdam, The Netherlands |
| |
Abstract: | We have used a continuous spectrofluorimetric method to analyse the role of cytosolic free Ca2+ ([Ca2+]i) in the lysosomal enzyme release from the azurophilic granules in human neutrophils stimulated with f-Met-Leu-Phe (fMLP) in the presence of cytochalasin B. Measurements were performed with the β-glucuronidase substrate 4-methylumbelliferyl-β--glucuronide. We found that the transient rise in [Ca2+]i induced by fMLP is a necessary signal to obtain to obtain maximal degranulation. When this Ca2+ transient is prevented by the Ca2+ chelator BAPTA, degranulation can still be induced by a stimulated Ca2+ influx, albeit to a lower extent. We also studied the degranulation process in the neutrophils of a patient with a generalized chemotactic defect. Release of β-glucuronidase from the patient's neutrophils could not be induced despite the occurrence of a normal Ca2+ response and normal degranulation of specific granules. We conclude that, besides an increase in [Ca2+]i], an additional signal is required for the fusion of azurophilic granules with the plasma membrane in human neutrophils. |
| |
Keywords: | Ca2+ homeostasis degranulation neutrophils β-glucuronidase |
本文献已被 ScienceDirect 等数据库收录! |