Effect of sodium ferulate on proliferation of normal rat chondrocytes. After chondrocytes had been cultured in a 96-well plate for 48 hours, 125, 250, 500 or 1,000 μmol/l sodium ferulate (SF) were added for 72 hours, respectively. Values represent mean ± standard error of the mean of eight different wells. **P < 0.01 versus control (0). OD, optical density.