MOVEMENT OF FIBRINOGEN RECEPTORS ON THE VENTRAL MEMBRANE OF SPREADINGPLATELETS

We have used fibrinogen-gold conjugates and fluorescein-labelled fibri nogen to examine the presence of fibrinogen receptors on the ventral m embrane of spreading platelets and to visualize the redistribution of the receptors during platelet spreading. The movement of fibrinogen-go ld conjugates was observed in real time using video-enhanced interfere nce reflection microscopy (VEIRM) and the redistribution of fluorescei n-labelled fibrinogen was examined using video-intensified epifluoresc ence microscopy (VIFM). Fibrinogen was picked up by spreading platelet s and moved rewards the centre of the platelets. The velocity of the m ovement of fibrinogen-gold conjugates under the ventral membrane range d from less than 0.1 mu m min(-1) to more than 10 mu m min(-1). The av erage velocity in the peripheral web region was more than 6 mu m min(- 1), and was reduced to around 1 mu m min(-1) in the outer and inner fi lamentous zones. The centralized fibrinogen molecules were internalize d and eventually removed from the platelets. Video microscopy in conju nction with colloidal gold particles provides a simple method for real -time observation of the movement of fibrinogen receptors on the ventr al membrane of spreading platelets. (C) 1998 Elsevier Science Ltd. All rights reserved.