TY - JOUR
T1 - Membrane microenvironmental changes during activation of human blood platelets by thrombin; A study with a fluorescent probe
AU - Nathan, I.
AU - Fleischer, G.
AU - Livne, A.
AU - Dvilansky, A.
AU - Parola, A. H.
PY - 1979/12/1
Y1 - 1979/12/1
N2 - Membrane microenvironmental changes associated with thrombin-induced platelet activation were followed by fluorescence intensity and polarization studies of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled human platelets. The labeling of washed platelets with DPH did not alter platelet intactness and morphology. In response to thrombin, DPH-labeled platelets exhibited reduced serotonin release, yet aggregation was barely inhibited. Shape change induced by thrombin or ADP was indistinguishable in control and in DPH-labeled platelets. During platelet aggregation induced by thrombin, fluorescence intensity increased by about 14%, which may indicate a more hydrophobic exposure of the probe. However, no change in fluorescence was detected during patelet shape change, induced either by thrombin in presence of EDTA or by ADP. Thrombin-activated platelets exhibited an increase in values of fluorescence polarization (P) during the stages of shape change and secretion, which further increased during aggregation. A similar pattern of increase in P values characterized platelet shape changes, caused either by thrombin in the presence of EDTA or by ADP. Changes in individual platelets are discernible from the alterations of the aggregating cells. These results may indicate that platelet activation is accompanied by an increase in rigidity of the membrane lipids. Functionally, the elevated 'microviscosity' may reflect a primary role of membrane lipids in modulating the process of platelet activation or secondary transitions in lipids due to membrane events mediated by proteins.
AB - Membrane microenvironmental changes associated with thrombin-induced platelet activation were followed by fluorescence intensity and polarization studies of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled human platelets. The labeling of washed platelets with DPH did not alter platelet intactness and morphology. In response to thrombin, DPH-labeled platelets exhibited reduced serotonin release, yet aggregation was barely inhibited. Shape change induced by thrombin or ADP was indistinguishable in control and in DPH-labeled platelets. During platelet aggregation induced by thrombin, fluorescence intensity increased by about 14%, which may indicate a more hydrophobic exposure of the probe. However, no change in fluorescence was detected during patelet shape change, induced either by thrombin in presence of EDTA or by ADP. Thrombin-activated platelets exhibited an increase in values of fluorescence polarization (P) during the stages of shape change and secretion, which further increased during aggregation. A similar pattern of increase in P values characterized platelet shape changes, caused either by thrombin in the presence of EDTA or by ADP. Changes in individual platelets are discernible from the alterations of the aggregating cells. These results may indicate that platelet activation is accompanied by an increase in rigidity of the membrane lipids. Functionally, the elevated 'microviscosity' may reflect a primary role of membrane lipids in modulating the process of platelet activation or secondary transitions in lipids due to membrane events mediated by proteins.
UR - http://www.scopus.com/inward/record.url?scp=0018614808&partnerID=8YFLogxK
M3 - Article
C2 - 489573
AN - SCOPUS:0018614808
SN - 0021-9258
VL - 254
SP - 9822
EP - 9828
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 19
ER -