Inhibitory effect of disodium quercetin-7,4'-disulfate on aggregation of pig platelets induced by thrombin and its mechanism.
OBJECTIVE
To study the inhibitory effect of semi-synthesized quercetin derivatives--disodium quercetin-7,4'-disulfate (DQD) on the platelet aggregation induced by thrombin and its mechanism.


METHODS
Platelet aggregation was analysed by turbidimetry. Cytosolic free calcium concentration ([Ca2+]i) was determined by Fura-2 fluorescence technique. Activity of Ca2+/PL dependent protein kinase C (PKC) was assayed by incubating PKC with histone III S and [gamma-32P]ATP. The cytoskeletal proteins were precipitated by Triton and separated by SDS-PAGE.


RESULTS
DQD inhibited the platelet aggregation induced by thrombin (500 U/L), when DQD concentrations were 100, 200, and 400 mumol/L, the inhibition rates were 77%, 86%, and 82% respectively. DQD inhibited Ca2+ influx in platelets induced by thrombin (500 U/L) in the presence of extracellular Ca2+ 1 mmol/L in a concentration-dependent manner (10-80 mumol/L); DQD also had inhibitory effect on intracellular Ca2+ mobilization in the absence of extracellular Ca2+. DQD (10-160 mumol/L) inhibited the cytosolic Ca2+/PL dependent PKC from platelets in a concentration-dependent manner, but had no effect on membrane PKC. DQD (20-200 mumol/L) inhibited the actin polymerization induced by thrombin (500 U/L) in platelets in a concentration-dependent manner.


CONCLUSIONS
DQD inhibited pig platelet aggregation induced by thrombin and its molecular mechanism was due to its inhibition of Ca2+ influx, intracellular Ca2+ mobilization, Ca2+/PL dependent PKC activity, and actin polymerization.
Liu
W
W
Institute of Biochemistry and Molecular Biology, Guangdong Medical College, Zhanjiang 524023, China. wenliu@gdmc.edu.cn
Liang
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D000199:Actins / Q000097:blood; D000818:Animals; D001693:Biological Transport, Active; D001792:Blood Platelets / Q000378:metabolism; D002118:Calcium / Q000097:blood*; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D010974:Platelet Aggregation / Q000187:drug effects*; D011493:Protein Kinase C / Q000097:blood; D011794:Quercetin / Q000031:analogs & derivatives / Q000494:pharmacology*; D013552:Swine
D000199:Actins; D005343:Fibrinolytic Agents; C437392:disodium quercetin-7,4'-disulfate; D011794:Quercetin; D011493:Protein Kinase C; D002118:Calcium