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

Tetramethylpyrazine (TMPZ) is an active ingredient of a Chinese herbal medicine (Ligusticum walchii Franchat). In this study, TMPZ (50-200 mu M) significantly 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 (15 and 30 min)-dependently triggered endothelial-type constitutive nitric oxide synthase (ccNOS) protein expression in human platelets. These results indicated that TMPZ at micromolar concentrations stimulated nitric oxide production in human platelets via a novel mechanism that activated ccNOS protein expression. (C) 2000 Elsevier Science Inc. All rights reserved.