Objective: To characterize vasodilatative effect of magnolin (Mag) on isolated rat thoracic aorta

elucidate its possible action mechanism

and its toxicity in rat renal cells NRK in vitro. Method: The thoracic aorta was isolated from male Sprague-Dawley (SD) rats and the isometric tension of aortic rings induced by phenylephrine (PE

1 μmol· L-1) were measured. To investigate the vasodilation effect of Mag on it were observed in the rings with endothelium intact or endothelium denuded. The rat renal cells NRK were cultured in vitro and MTT assay. Result: Mag (0.1-1 000 μmol· L-1) produced concentration-dependent response

relaxations in PE-contracted aortic rings with endothelium. The half maximal effective concentration (EC50) of Mag was 24.43 μmol· L-1. The vasodilatative effect by Mag was not statistically inhibited by 100 μmol· L-1 (L-NAME) in the preparations with endothelium. The relative growth rates (RGR) of Mag (0.1-1 000 μmol· L-1) were between 84.17% and 134.60%. Conclusion: Magnolin causes relaxation of aortic ring through endothelium-dependent pathway. The mechanisms might be involved in eNOS. Magnolin is safe to rat renal cells NRK with concentration between 0.1 μmol· L-1and 1 000 μmol· L-1.