Abstract: Objective To investigate the effect of nicotine on the proliferation and apoptosis of rats’ aortic vascular smooth muscle cells (VSMCs) in order to demonstrate the mechanism of the smoking-induced the progress and mechanism of the atherosclerosis. Methods VSMCs isolated from rats were subjected to 100 μmol/L nicotine for 24 hours，and the cells without nicotine were used as control. The morphology of apoptotic cells was observed by the fluorescence microscope and scanning electron microscopy. The rate of cell apoptosis and proliferation was analyzed by flow cytometry (FCM). And also the proliferation of vascular smooth muscle cells was detected by BrdU(bromodeoxyuridine)-ELISA kit. Results Compared with the control group (14.46% ± 4.47%), the percent of S-phase cells in nicotine group reduced (6.77% ± 3.41%). The rate of the apoptosis VSMCs in control group was 11.47% ± 2.56%, which was lower than that in 100 μmol/L nicotine group (24.65%±4.67%, P<0.05). The DNA content detected by BrdU-ELISA in the nicotine group was remarkably lower than that in control group (P<0.05). Moreover, there were more cell apoptosis bodies and nucleorhexis in nicotine group than that in control group detected by cytochemical staining method and scanning electron microscope.Conclusion It is concluded that the steady dose

Key words: Vascular smooth muscle cell, Nicotine, Proliferation, Apoptosis, Flow cytometry, Scanning electron microscope, Rat