Planta Med. 2003 Jun; 69(6): 557-8.

Tetramethylpyrazine as potassium channel opener to lower calcium influx into cultured aortic smooth muscle cells.

Tsai CC, Lai TY, Huang WC, Yang T, Liu IM, Wong KL, Chan P, Cheng JT.

Department of Traditional Medicine, School of Post-Baccalaureate Chinese Medicine, China Medical College, Taichung City, Taiwan. tsaic@mail.cmc.edu.tw

In the present study, the effect of tetramethylpyrazine (TMP) on calcium (Ca 2+) influx was investigated in cultured vascular smooth muscle (A7r5) cells using Fura-2 as an indicator. The increase of Ca 2+ concentration in A7r5 cells produced by vasopressin or phenylephrine was attenuated by TMP from 0.01 micromol/L to 1 mmol/L. The decrease in the intracellular potassium concentration in A7r5 cells by TMP from 0.01 micromol/L to 10 micromol/L was characterized using PBFI/AM. Inhibitors specific to the small conductance calcium-activated potassium (SKCa ) channel or the ATP-sensitive potassium (K ATP ) channel abolished the actions of TMP. The obtained results indicate that the decrease of Ca 2+ influx into A7r5 cells by TMP is mainly mediated by the opening of potassium channels.