Thrombin-induced human platelet aggregation is inhibited by protein-tyrosine kinase inhibitors, ST638 and genistein.
We have investigated the involvement of protein-tyrosine kinases in thrombin-induced aggregation of human platelets, using ST638 and genistein which are known inhibitors of protein-tyrosine kinase. Preincubation of platelets with 50 microM of ST638 or 25 micrograms/ml of genistein completely blocked the platelet aggregation induced with 0.05 unit/ml of thrombin. The increase of protein-tyrosine phosphorylation bands (135-, 124-, 76-, 64-, and 60-kDa) induced with thrombin was also inhibited by these inhibitors in a dose-dependent manner. These inhibitors also blocked the platelet aggregation and protein-tyrosine phosphorylation induced with thrombin in aspirin-treated platelets. Increase of the intracellular Ca2+ concentration induced by thrombin was also inhibited by higher concentrations of genistein. These results suggest that the protein-tyrosine phosphorylation plays a certain role in platelet activation having some relation to the intracellular Ca2+ concentration.
Asahi
M
M
Department of Biochemistry, Fukui Medical School, Japan.
Yanagi
S
S
Ohta
S
S
Inazu
T
T
Sakai
K
K
Takeuchi
F
F
Taniguchi
T
T
Yamamura
H
H
D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D001798:Blood Proteins / Q000302:isolation & purification / Q000378:metabolism; D002118:Calcium / Q000097:blood; D002934:Cinnamates / Q000494:pharmacology*; D019833:Genistein; D006801:Humans; D066298:In Vitro Techniques; D007529:Isoflavones / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000097:blood / Q000302:isolation & purification; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D013440:Sulfides / Q000494:pharmacology*; D013917:Thrombin / Q000494:pharmacology*
D001798:Blood Proteins; D002934:Cinnamates; D007529:Isoflavones; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D013440:Sulfides; C060747:ST 638; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D013917:Thrombin; D002118:Calcium