Effect of tetramethylpyrazine on blood pressure in hypertensive rats and calcium mobilization in vascular smooth muscle cells

Background: Tetramethylpyrazine (TMP) is a plant alkaloid isolated from the traditional Chinese herb Chuang Xiong. It has been proved to have antihypertensive effect on anestheized animals. This study was undertaken to evaluate its effect on ambulatory hypertensive rats and its mechanism of antihypertension. Materials and Methods: Deoxycorticosterone acetate (DOCA)- induced hypertensive rats comprising 4 groups (each n = 8) were used for study. TMP dissolved in normal saline was given intraperitoneally at different dosages (1,5,10 mg/kg) and blood pressure was recorded by a noninvasive tail-cuff monitor. Aortic smooth muscle cells (A7r5) were employed to evaluate calcium influx inhibition by using Fura-2 calcium-sensitive dye. Results: The hypotensive effect of TMP on DOCA-salt sensitive hypertensive rats was dose-dependent; the maximal blood pressure decrease was 28.2 ± 5.0 mm Hg at the dosage of 10 mg/kg. By using calcium influx stimulating agents phenylephrine (an α adrenergic agonist) and arginine vasopressin to induce calcium influx, TMP showed a dose-dependent calcium influx inhibition. Conclusion: TMP isolated from traditional herb has an effective antihypertensive action and this antihypertension is probably due to intracellular calcium influx inhibition.