Figure 6. Protein expression of P16 and P21 in rabbit AFSCs cultured in growth medium with five different conditions for 6 days and tested by western blot. (A) Protein levels for P16, P21 and GAPDH; (B) semi-quantification of P16; (C) semi-quantification of P21. To ensure that equal amount of total protein was loaded, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was used as a loading control for protein normalization. The results indicated that bleomycin increased both P16 and P21 protein expression in AF cells with a concentration-dependent manner. Adding rapamycin in bleomycin treated AF cells decreased P16 and P21 levels in AF cells. *p<0.05 compared to control, #P<0.05 compared to the cells treated with 50 μg/ml of bleomycin.