Figure 4.

Glycyrrhetinic acid (GA) induces endoplasmic reticulum (ER) stress. (A) A549 and NCI-H460 cells treated with various concentrations of GA (12.5, 25 and 50 μmol/l) for 24 h were analyzed by immunoblotting with antibodies against Bip, protein kinase-like ER kinase (PERK) and ERP72. β-actin was used as a loading control. (B) Densitometry analysis of Bip, PERK and ERP72 levels relative to β-actin were performed using three independent experiments. Error bars represent SD; ^*p<0.01, ^#p<0.05.