Aim To investigate the effects of intermittent high glucose on cell proliferation and the expressions of apoptosis proteins in rat vascular smooth muscle cells(VSMC).Methods Rat VSMC were incubated with constant high glucose or intermittent high glucose.VSMC proliferation was evaluated by MTT assay.The cell cycle was examined by flow cytometry.The protein expressions of Bcl-2 and Bax were studied by Western blotting.Results Compared with constant high glucose,intermittent high glucose significantly stimulated cell proliferation,enhanced transition of cultured VSMC from the G0/G1 phase to the S phase and upregulated the ratio of Bcl-2/Bax.Conclusions Intermittent,rather than constant,high glucose,could significantly promote VSMC proliferation and induce apoptosis by regulating the cell cycle and modulating the apoptosis-regulatory proteins,indicating its stronger proatherogenic role in diabetic macrovascular disease.