Changes of acid SMase activity in Caco-2 cells treated with AKBA. (A): The cells were treated with AKBA in different concentrations for 24 h and acid SMase activities in cell lysate were determined. (B): The cells were treated with AKBA (50 μM) or without AKBA as control for different times. After treatment, the enzyme activity was determined in comparison with the control group at each time point. The activities were adjusted to protein levels in the cells and expressed as percentage of the control. Results are mean ± standard error from 3 separated experiments. * P < 0.05, **P < 0.01, and *** P < 0.001 compared with the control.