The mechanism of vasorelaxation induced by Schisandra chinensis extract in rat thoracic aorta.
OBJECTIVE
Schisandra chinensis (SC) is a known medical herb for the treatment of cardiovascular symptoms associated with menopausal symptoms in Korea. However, the pharmacological action mechanisms involved have not been well studied. This study was aimed to investigate the vascular effects of SC in rat thoracic aorta.


METHODS
We isolated the hexane, chloroform, and methanol extracts from SC and evaluated their vasodilatory effects in the rat thoracic aorta.


RESULTS
Hexane extracts of SC (SCHE, 5 x 10(-5) to 10(-3) g/L) caused a concentration-dependent relaxation in both endothelium-intact and -denuded aortas. The relaxant effect of SCHE on the endothelium-intact aorta was more prominent than on the endothelium-denuded aorta. The former was significantly attenuated by L-NAME, a nitric oxide synthase inhibitor, and ODQ, a soluble guanyl cyclase inhibitor, but not by tetraethylammonium, a nonselective blocker of K(+) channels, and indomethacin, a cyclooxygenase inhibitor. Furthermore, SCHE caused nitrite production as well as eNOS activation in aortic segments, suggesting implication of NO signal pathway in SCHE-induced relaxation. In endothelium-denuded aorta, SCHE-induced vasorelaxation was also attenuated by calyculin A, an inhibitor of myosin light chain (MLC) phosphatase, but not by ML-9, a MLC kinase inhibitor, suggestive of implication of MLC phosphatase activation. Phenylephrine-enhanced MLC phosphorylation ratio was significantly attenuated by SCHE, which was recovered to the control level by pretreatment with calyculin A.


CONCLUSIONS
Taken collectively, these findings suggest that the vascular relaxation evoked by SCHE was mediated by not only endothelium dependent NO pathway but also direct effect on vascular smooth muscle cell via dephosphorylation of MLC.
Park
Ji Young
JY
Department of Pharmacology, College of Medicine, Pusan National University, Busan 602-739, Republic of Korea.
Shin
Hwa Kyoung
HK
Lee
You Jin
YJ
Choi
Young Whan
YW
Bae
Sun Sik
SS
Kim
Chi Dae
CD
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D005638:Fruit / Q000737:chemistry; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D010766:Phosphorylation; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D032141:Schisandra / Q000737:chemistry*; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D010936:Plant Extracts; D009569:Nitric Oxide; D009219:Myosin-Light-Chain Kinase; D043263:Myosin-Light-Chain Phosphatase