|
The present study was attempted to investigate the effects of total ginseng saponin (GTS), panaxadiol-type (PDS) and panaxatriol-type saponin (PTS) on contractile responses of vasoconstrictors in aortic smooth muscle stripes of normotensive (NR) and spontaneous hypertensive rats (SHR). Phenylephrine (an adrenergic α1-receptor agonist) and high potassium (a membrane depolarizing agent) caused greatly contractile responses in both NR and AHR aorta, respectively. Phenylephrine- and high potassium-induced contractile responses were greater in NA than those in SHR aortic smooth muscle stripes. In NR, the contractile responses of high potassium (5.6×10.2 M) were not affected in the presence of GTS (300 μg/ml), PDS (300 μg/ml), and PTS (300 μg/ml), respectively whereas phenylephrine (10.6 M)-induced contractile responses were markedly inhibited. In SHR, the contractile responses of high potassium (5.6×10.2 M) were not affected in the presence of GTS (300 μg/ml), PDS (300 μg/ml), and moderate doses of PTS (150-300 μg/ml), respectively but greatly blocked by high concentration of PTS (600 μg/ml). Phenylephrine (10.6 M)-induced contractile responses were inhibited in a dose dependent fashion (150-600 μg/ml) by the pretreatment with PTS while not altered in the presence of GTS (300 μg/ml) and PDS (300 μg/ml), respectively. Taken together, these experimental results suggest that ginseng saponins cause vascular relaxation through blockade of adrenergic α1-receptors and some unknown mechanisms, and that there is some difference in sensitivity of vascular smooth muscle between NR and SHR in responses to ginseng saponins. It seems that panaxatriol type of some ginseng saponins has the greatest potency in vascular relaxation.
|