The effect of canarium pimela koening leaves on rat thoracic aorta smooth muscle cells

Objective To investigate the relaxative characteristics and mechanism of the aqueous soluble part of extracts from Canarium pimela Koening leaves on rat thoracic aortic artery.Methods We perfused the isolated rings and observed the response of norepinephrine(NE)or KCl-induced artery contraction to the extracts,its relationship with adrenergic receptor and intracellular and extracellular calcium-dependent vascular constriction.Same methods were used to study the constriction response of vascular ring to NE.Results The extracts from Canarium pimela Koening leaves relaxed rat aorta rings pre-contracted with NE in a dose-dependent manner.This effect was not inhibited by metoprolol;When the endothelium of rat thoracic was removed,the extracts had no significant effects on aorta rings pre-contraction with NE.The extracts had a suppressive effect on the aorta contraction induced by extracellular calcium and shortened the duration of aorta maximum continuous contraction induced by intracellular calcium,but had no effect on its tension.However,the effect was not attenuated by co-incubation with heparin and Ca2+-free medium.The extracts could further elevate aorta rings tension in pre-contraction with KCl(30 and 80 mmol/L).This effect was not inhibited by phentolamine.Conclusion The extracts can relax rat thoracic aorta rings without endothelium.The mechanism is associated with activating β-receptor,opening of Ca2+ channel by the receptor dependent pathway as well as inhibition of Ca2+ influx in vascular smooth muscle cell.The extracts also increases aorta rings tension in pre-contraction with KCl,but is not associated whit α-receptor.