legend: Cell viability analysis. A) Cell viability assessed by MTT assay. DMSO, cells treated with dimethyl sulfoxide (1 μl/ml); TM1, cells treated with 1 μg/ml tunicamycin; TM10, cells treated with 10 μg/ml tunicamycin. TM + TD, cells treated with 10 μg/ml TM and TUDCA at indicated doses. Data shown are representative of 6 separate experiments and values are given as mean ± SD. Statistical analysis was performed by one way analysis of variance with all pairwise multiple comparison procedures done by Tukey test. *, p < 0.001 vs. 18h control. **, p < 0.001 vs. 18h control, 18h DMSO, 18 h TM1, 18 h TM + TD 0.5 mM and 18 h TM + TD 0,75 mM #, p < 0.001 vs. 24h control, 24 h DMSO and 24 h TM + TD 0.5 mM ##, p < 0.001 vs. 24h control, 24h DMSO, 24 h TM1, 24 h TM + TD 0.5 mM and 24 h TM + TD 0,75 mM+, p < 0.001 vs.48h control. B) Dose-dependent effect of TUDCA on cell viability at 24 h time-course. C, control. Data shown are representative of 3 separate experiments and values are given as mean ± SD. No significant difference was observed in cell viability among the different dose groups. C) Morphological changes of ARPE-19 cells observed under an inverted light microscope (20× magnification). Cells were treated with 1 μl/ml DMSO; 0.5 mM taurohyodeoxycholic acid (TUDCA); 10 μg/ml tunicamycin (TM) and 10 μg/ml TM + 0.5 mM TUDCA for 24 h. Cells treated with 10 μg/ml TM showed morphological changes such as cell shrinkage, detachment and rounding. A decrease in cell population was also noted in the TM group.