Vascular dilation by paeonol--a mechanism study.
The goal of this study was to investigate the mechanism underlaying the vasodilatory effect of paeonol, a major active element from the root bark of Chinese herbs Paeonia suffruticosa Andr. and Cynanchum paniculatum (Bunge) Kitagawa. Paeonol relaxed isolated rat aorta rings by 95.6% while the 10(-6) M forskolin-induced vasodilatation used as 100%. The EC(50) of vasodilatation by paeonol is 2.9x10(-4) M. Although paeonol exerted endothelium-independent relaxation, L-NAME treatment inhibited paeonol-induced vasodilation of endothelium intact rings, while indomethacin did not. Both L-NAME and ODQ did not affect paeonol relaxation in the rings without endothelium. In addition, paeonol markedly elevated NO generation in cultured endothelial cells. Pre-treatment of propranolol, glibenclamide, TEA and BaCl(2) did not affect paeonol relaxation of endothelium removed rings. On the other hand, pre-treated of rings (without endothelium) with paeonol markedly blocked vasoconstriction induced by AngII, PGF(2alpha), 5-HT, dopamine, vasopressin, endothelin-1 and PE. The paeonol incubation also significantly attenuated KCl-induced contraction which mainly depended on Ca(2+) influx. In Ca(2+)-free medium (containing 10(-4) M of EGTA and 60 mM of KCl), paeonol suppressed the contraction curve of CaCl(2). In addition, paeonol also inhibited contraction by PE in Ca(2+) free solution (containing 10(-4) M of EGTA) which mainly relied on intracellular Ca(2+) release. Whole-cell patch-clamp experiment showed that paeonol shifted the I-V curve and the peak value of calcium currents was significantly inhibited. In conclusion, our study suggested that voltage-dependent and receptor-operated Ca(2+) channel, as well as intracellular Ca(2+) release were all inhibited by paeonol. An intracellular Ca(2+) regulatory mechanism may be responsible to potent vasodilatory effect of paeonol.
Li
Ya-juan
YJ
Murad Research Institute for Modernized Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, PR China.
Bao
Jun-Xiang
JX
Xu
Jin-wen
JW
Murad
Ferid
F
Bian
Ka
K
D000098:Acetophenones / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology; D002122:Calcium Chloride / Q000494:pharmacology; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D000098:Acetophenones; D015220:Calcium Channels; D014665:Vasodilator Agents; C013638:paeonol; D004533:Egtazic Acid; D011189:Potassium Chloride; D002122:Calcium Chloride; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester