The antiplatelet activity of tetramethylpyrazine is mediated through activation of NO synthase

Tetramethylpyrazine (TMPZ) is an active ingredient of a Chinese herbal medi cine (Ligusticum walchii Franchat). In this study, TMPZ (50-200 mu M) signi ficantly increased production of nitrate and cyclic GMP in human platelets within a 15-min incubation period. TMPZ concentration-dependently inhibited intracellular Ca2+ mobilization in human platelets stimulated by collagen (5 mu g/ml). Furthermore, TMPZ concentration (50 and 200 mu M)- and time (1 5 and 30 min)-dependently triggered endothelial-type constitutive nitric ox ide synthase (ccNOS) protein expression in human platelets. These results i ndicated that TMPZ at micromolar concentrations stimulated nitric oxide pro duction in human platelets via a novel mechanism that activated ccNOS prote in expression. (C) 2000 Elsevier Science Inc. All rights reserved.