Fig. 3.

a Effect of piperine (PIP) on tunicamycin (TM)-induced loss of cell viability (measured by MTT assay) in NRK-52E cells. Values were normalized to DMSO-treated control and expressed as mean ± SEM (n = 3). b Effect of piperine (PIP) on tunicamycin (TM)-induced expression of GRP78 and CHOP expression in NRK-52E cells as determined by western blotting and quantified using densitometry (c, d). Values were normalized to β-actin and expressed as percentage of DMSO-treated control for GRP78 and percentage of tunicamycin (TM)-treated group for CHOP (mean ± SEM; n = 3). #P < 0.05 compared to DMSO-treated control group; *P < 0.05 compared to TM-treated group