The rats were intragastrically administered with 3 ml of piperonylic acid (10 g/L) daily

VSMCs were inoculated on 96-well culture plates (1×10^6/L), and the culture medium was refreshed after 48 h and then discarded when 90 % of the cells fused, with serum-free DMEM culture medium used instead. The cells were then starved for 48 h to be synchronized in the G0 phase. 50 μl of pH7.4 PBS was added into each well of the control group, 5 % FBS was added into the FBS group, and piperonylic acid solutions (fi nal concentrations: 20, 40, 60, 80 mg/L) were added into each well of each experimental group respectively. 48 h later, 3H-TdR (3.0×105 Bq/L) was added, 48 h after which the cells were collected. Then the cell membrane was broken, and 3 ml of scintillating solution were added. The radiation intensity was measured by liquid scintillation counting.