DYNAMIC REORGANIZATION OF THE ALKALINE PHOSPHATASE-CONTAINING COMPARTMENT DURING CHEMOTACTIC PEPTIDE STIMULATION OF HUMAN NEUTROPHILS IMAGED BY BACKSCATTERED ELECTRONS

Scanning electron microscopy (EM) and cytochemical techniques were use d to examine the alkaline phosphatase-containing compartment in human neutrophils after stimulation with nanomolar concentrations of N-formy lmethionyl-leucyl-phenylalanine (10(-8) M fMLP). Alkaline phosphatase (AlkPase) activity was demonstrated with a lead-based metal capture cy tochemical method. The reaction product was visualized with the backsc attered electron imaging mode of scanning EM, and analyzed by electron probe X-ray microanalysis. Alkaline phosphatase activity was detected only in fMLP-stimulated neutrophils; unstimulated neutrophils display ed no activity. Stimulation of human neutrophils with 10(-8) M fMLP in duced a time-dependent intracellular redistribution of irregular round or tubular granules containing alkaline phosphatase activity, as seen by backscattering. The intracellular redistribution of alkaline phosp hatase activity was accompanied by increased cytochemical activity on the cell surface. The reaction product was localized preferentially on ridges and folds of polar neutrophils. Reorganization of the AlkPase- containing compartment correlated with changes induced by fMLP in cell shape, ie, membrane ruffling and front-tail polarity, as as observed with the secondary electron image mode of scanning EM. These findings demonstrate the intracellular reorganization, increase, and asymmetric distribution of alkaline phosphatase activity on the plasma membrane of human neutrophils after stimulation by chemotactic peptides.