title: Platelet activation studied by fluorescence polarization.
abstract: Platelet activation was elevated by changes in the fluorescence anisotropy of the sulfhydryl-reactive fluorescent probe, (5-[2-(iodoacetyl) aminacetyl]aminonaphthalene-1-sulfonic acid. The membrane-permeable fluorophore was shown to bind to a multitude of cytoplasmic and membrane proteins. Platelets were stimulated by addition of thrombin, arachidonic acid or ADP under conditions that did not induce aggregation. A sudden increase in the fluorescence anisotropy, r of moderate degree (25-33%) occurred during the first 60 s after exposure of platelets to the aggregating agents and was sustained during the entire period of observation (15-18 min). Phenylmethylsulfonyl thrombin was unable to produce these changes in fluorescence anisotropy. Preincubation of platelets with colchicine reduced r within 30-60 s after platelets were exposed to thrombin. These findings are interpreted as an indication of a general decrease in the 'motional freedom' of the fluorophores and indirectly their ligand molecules.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure; D003078:Colchicine / Q000494:pharmacology; D005454:Fluorescence Polarization; D006801:Humans; D008970:Molecular Weight; D010974:Platelet Aggregation; D013439:Sulfhydryl Reagents; D013917:Thrombin / Q000494:pharmacology
chemical_list: D001095:Arachidonic Acids; D013439:Sulfhydryl Reagents; D016718:Arachidonic Acid; D000244:Adenosine Diphosphate; D013917:Thrombin; D003078:Colchicine