Trifluoperazine inhibition of fibrinogen receptor redistribution in surface activated platelets: correlative video-enhanced differential interference contrast light microscopic, high voltage electron microscopic and scanning electron microscopic studies.

Video-enhanced differential interference contrast (VDIC) light microscopy in conjunction with fibrinogen labelled colloidal gold was employed as a probe to follow the mobility of the fibrinogen receptor on platelets. Correlative studies by both high voltage and scanning electron microscopy confirms localization of labels relative to platelet ultrastructural and surface characteristics, respectively. Treatment of platelets with trifluoperazine prior to and after incubation with fibrinogen-gold labels results in a concentration dependent inhibition of receptor movement. The results obtained from this study suggest that phosphorylation of myosin by the Ca++-calmodulin dependent enzyme, myosin-light chain kinase, is important in the fibrinogen redistribution that occurs during platelet activation.