Study On The Effect And Mechanism Of Vindorosine-induced Relaxation In Rat Renal Arteries

Hypertension is a common disease threatening the life and health of human being. Despite the existing of more than one hundred kinds of therapeutic drugs in clinic, the control of which is suboptimal for the general population. Catharanthus roseus(L.) G. Don is a traditional herbal medicine used in Asian and African countries for the treatment of various diseases including hypertension, whose active components and mechanisms remain unclear. Given the importance of dilating vessels, relieving the pressure of vascular wall and local shortage of blood supply in the preventing and treatment of hypertension, this study screened some components from Catharanthus roseus(L.) G. Don and first found that vindorosine has a potent relaxing effect in rat renal arteries. Additionally, the underlying mechanisms were investigated.Aim: To screen these dilating components from Catharanthus roseus(L.) G. Don. The present study focuses on exploring the cellular mechanisms for the vasodilatation of rat renal artery induced by vindorosine extracted from Catharanthus roseus.Methods: In experiments, intrarenal arteries isolated from 200-300 g weight male adult Sprague-Dawley(SD) rats and different agonists and inhibitors related to endothelium, K+ channels, Ca2+ channels and important protein, were prepared and used for vascular contraction and relaxation activity measurement by DMT capillary tension in vitro assay system and Power Lab inputs data acquisition systems. Fluorescein labeling and laser scanning confocal were utilized to determine Ca2+ trend of vascular smooth muscle cells(VSMCs).Results: Vindorosine acted as vasodilator at micromolar range to dilate renal arteries pre-contracted by KCl, phenylephrine, U46619, and serotonin. Vindorosine-induced relaxations were unaffected neither by endothelium denudation nor by treatment with nitric oxide synthase inhibitor L-NAME, guanylyl cyclase inhibitor ODQ, cyclooxygenase inhibitor indomethacin, or K+ channel blockers including tetraethylammonium ions(TEA+), glibenclamide, and Ba Cl2. The relaxations were attenuated in the presence of 0.1 μM nifedipine(L-type Ca2+ channel blocker). Vindorosine also concentration-dependently suppressed contraction induced by Ca Cl2(0.01-5 m M) in Ca-free 60 m M KCl solution. Furthermore, fluorescence imaging using fluo-4 demonstrated that 30 min-incubation with 100 m M vindorosine reduced 60 m M KCl-induced Ca2+ influx in smooth muscle of rat renal arteries. Moreover, the pretreatment of KV channels blocker 4-AP showed partial inhibition to vasodilation of vindorosine. Vindorosine-caused vasorelaxation was partly weakened by pre-incubation of PKC inhibitor Ro-32-04323 while Rho-kinase inhibitor Y-27632 did not cause any effect on vindorosine compared with control. Meanwhile,PKC agonist PMA was used to stimulate a Ca2+-independent contraction in artery ring and behaved ineffective to PMA-induced contraction.Conclusion: The study for the first time reports the vasorelaxant effect of vindorosine in rat renal artery and declares the underlying mechanisms involves the inhibition of Ca2+ entry via L-type Ca2+ channels, participation of KV channels and PKC in vascular smooth muscle.