Fig. 3.

Human SH-SY5Y neuroblastoma cells express the neuron-specific marker GAP-43. Human SH-SY5Y neuroblastoma cells were grown to 80% confluency onto cell culture Petri dishes in normal serum. Then, cells were subjected to medium replacement containing N: normal serum or L: low serum. Both cultures were supplemented with 15 μM RA as described in “Materials and methods” section. Chronic RA treatment was performed by replacing the corresponding medium with fresh medium supplemented with 15 μM RA every 2 days. On the corresponding experimental day, cells were lysed and the GAP-43 protein levels were determined by western blot analysis of whole-cell lysates. Non-RA treated cells (undifferentiated cells) at experimental day 0 served as controls. GAP-43 expression was normalized to β-actin protein. Data are the means ± SEM of values from three independent experiments. There was no significant change in the expression of GAP-43 protein over the period and conditions assessed (P > 0.05 one-way ANOVA). Representative gels are shown