2.3. Assay of Cell Viability

The cell viability was measured using the MTT assay [31]. In brief, EA.hy926 cells (1x10⁴ cells/well) were cultured in a 96-well plate for 24 h at 37°C and then pretreated with RA (0-100 μM) for the next 24 h. After incubation, the medium was replaced by MTT solution (5 mg/ml) and kept in a humidified 5% CO₂ atmosphere for 4 h at 37°C. 100 μl of DMSO was added to all the wells and mixed thoroughly and read at 570 nm by a microplate reader (TECAN, Switzerland).

To study the effect of RA on ER stress-induced cell death, the cells were pretreated with RA (0-100 μM) for at least 24 h trailed by TPG (2 μM) for 2 h. The assay of MTT was then carried out as described above.