Inhibitory effects of sodium quercetin monosulfate on pig platelet aggregation induced by thrombin.
OBJECTIVE
To study the inhibitory effects of sodium quercetin monosulfate (SQMS) on pig platelet aggregation induced by thrombin.


METHODS
Platelet aggregation was analyzed by turbidimetry. Cytosolic free calcium concentration ([Ca2+]i) was determined by Fura-2 fluorescence. Activity of protein kinase C (PKC) was assayed by incubating PKC with histone III S and [gamma-32 P] ATP. The cytoskeletal proteins were precipitated by Triton X-100 and separated by SDS-PAGE.


RESULTS
SQMS inhibited the platelet aggregation induced by thrombin 500 U.L-1 with IC50 132 (50-347) mumol.L-1. SQMS inhibited Ca2+ influx in blood platelets induced by thrombin 500 U.L-1 in the presence of extracellular Ca2+ 1 mmol.L-1 with IC50 20 (9-46) mumol.L-1; SQMS inhibited the internal Ca2+ release in the absence of extracellular Ca2+. SQMS also decreased [Ca2+]i level in quiescent blood platelets. SQMS (10-160 mumol.L-1) inhibited the activity of cytosolic PKC from blood platelets in a concentration-dependent manner, but had no effect on membrane PKC. SQMS (20-80 mumol.L-1) inhibited the actin polymerization induced by thrombin 500 U.L-1 inblood platelets in a concentration-dependent manner.


CONCLUSIONS
SQMS inhibited pig platelet aggregation induced by thrombin and its mechanism might be due to its inhibitions of Ca2+ influx, internal Ca2- release, PKC activity, and actin polymerization.
Liu
W
W
Institute of Medical Biochemistry, Guangdong Medical College, Zhanjiang, China.
Song
Z J
ZJ
Liang
N C
NC
She
J
J
Mo
L E
LE
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000097:blood*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011493:Protein Kinase C / Q000097:blood; D011794:Quercetin / Q000031:analogs & derivatives / Q000494:pharmacology*; D013552:Swine; D013917:Thrombin / Q000494:pharmacology
D000199:Actins; D010975:Platelet Aggregation Inhibitors; D011794:Quercetin; D011493:Protein Kinase C; D013917:Thrombin; D002118:Calcium