These results suggested that the vasorelaxant effect of HHC is mediated by endothelium-independent pathway, probably due to inhibition of extracellular Ca+ influx through ROCC and VOCC, inhibition of Ca+ mobilization from intracellular stores as well Inhibition of PKC mediated Ca+-independent contraction. Moreover, HHC produces vasorelaxant effects probably by stimulating the sGC enzyme and β-adrenergic receptor.