Calcium influx inhibition: Possible mechanism of the negative effect of tetrahydropalmatine on left ventricular pressure in isolated rat heart

The active ingredient dl-tetrahydropalmatine (THP) isolated from the tradit ional Chinese herb Corydalis racemosa has been found to have antihypertensi ve effects. However, severe cardiac and neurological toxic effects were rep orted from using this herb for the treatment of pain. In an isolated perfus ed rat heart model, THP at the concentration of 100 mu M was found to have a negative effect (- 45 %) on left ventricular pressure and this effect was produced concentration-dependently from concentrations lower than 50 mu M. In isolated cardiomyocytes, radioactive calcium influx was also inhibited significantly by THP at the concentration of 100 mu M and this effect was a lso in a concentration-dependent manner (- 39 %). In a patient with latent heart disease, the use of Corydalis should probably be detrimental, the tox ic effect was probably due to calcium influx inhibition.