Endothelium-independent vasorelaxation by Ligusticum wallichii in isolated rat aorta: comparison of a butanolic fraction and tetramethylpyrazine, the main active component of Ligusticum wallichii.
Ligusticum wallichii is an herb widely used to treat vascular disorders in Asian countries, and tetramethylpyrazine (TMP) has been identified as one of its vasorelaxant active components. This study was performed to examine the endothelium-independent relaxation produced by the butanol-soluble fraction of L. wallichii extract (LwBt) and its possible mechanisms of action in isolated rat aortic rings. The effects were compared with those of TMP. LwBt produced vasorelaxation that increased gradually after 2-3 min of LwBt administration and reached a maximum within 30 min. LwBt-induced relaxation was significantly attenuated by pretreatment with 4-aminopyridine and apamin. Additionally, LwBt attenuated CaCl(2)-induced vasoconstriction in high-potassium depolarized medium. Thus, LwBt-induced vasorelaxation apparently involved inhibition of calcium influx, mediated by the opening of voltage-dependent and/or Ca(2+)-activated potassium channels. On the other hand, the effect of TMP was significantly attenuated by pretreatment with glibenclamide, and 4-aminopyridine had no effect. In conclusion, LwBt-induced endothelium-independent vasorelaxation was mediated by the opening of voltage-dependent potassium channels, while TMP-induced relaxation was mediated by the opening of ATP-dependent potassium channels. These effects of LwBt may be due to a substance other than TMP.
Kim
Eun-Young
EY
Food Function Research Division, Korea Food Research Institute, Gyeonggido 463-746, Korea.
Kim
Jung-Hyun
JH
Rhyu
Mee-Ra
MR
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism; D000440:Butanols / Q000737:chemistry; D004365:Drugs, Chinese Herbal / Q000302:isolation & purification / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D030004:Ligusticum / Q000737:chemistry*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors; D011719:Pyrazines / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D000440:Butanols; D004365:Drugs, Chinese Herbal; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D011719:Pyrazines; D014662:Vasoconstrictor Agents; C017953:tetramethylpyrazine