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Thromboxane A2 stimulates mitogen-activated protein kinase and arachidonic acid liberation in rabbit platelets
S Ohkubo1, N Nakahata, Y Ohizumi
1Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University Aoba, Sendai, Japan.
Abstract:
U46619, a thromboxane A2 mimetic, caused tyrosine phosphorylation of several proteins in rabbit platelets. Among them, 42 kDa protein was identified as a mitogen-activated protein kinase (MAPK). U46619 activated MAPK in a concentration-dependent manner, measured by incorporation of 32P to a specific substrate for MAPK. U46619 also liberated [3H] arachidonic acid in a concentration-dependent manner. The U46619-induced MAPK activation and [3H]arachidonic acid liberation were inhibited by SQ29548 and by the removal of external Ca2+ ions. This is a first demonstration that TXA2 activates MAPK accompanied with arachidonic acid liberation in rabbit platelets.