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.