Effects of Bisphenol A on apoptosis of spermatogenic cells and expression of Bax and Bcl-2 proteins in the Siberian frog Rana chensinensis

In order to investigate the effects of bisphenol A (BPA) on apoptosis and the expression levels of Bax and Bcl-2 protein in amphibian spermatogenic cells, we treated Rana chensinensis with concentrations of 10-7, 10-6, 10-5mol/L BPA respectively. Testes were removed after R.chensinensis had been treated for 3 , 5 or 7 days. Apoptotic cells were examined by TUNEL and Methyl Green-Pyronine. The expression levels of Bax and Bcl-2 protein in spermatogenic cells were detected by immunohistochemical staining. The results show that apoptotic index （AI）of spermatogenic cells of R.chensinensis treated with BPA is significantly higher than that of the control groups. AI of spermatogenic cells in 10-6 and 10-7 mol/L BPA groups are similar (P>0.05), but AI in 10-5 mol/L is significantly higher than that of in 10-6 and 10-7 mol/L BPA groups (P<0.05). AI of spermatogenic cells increases with prolonged treatment. The relative intensity of Bax immunostaining in BPA treated groups is higher than that of control groups (P<0.05) while the relative intensity of Bcl-2 in BPA treated groups is lower than that of control groups (P<0.05). Positive correlations exist between the AI of spermatogenic cells and the expression ratio of Bax/Bcl-2. These results indicate that BPA can enhance the apoptosis of spermatogenic cells in R.chensinensis, and that the change of the expression ratio of Bax /Bcl-2 might have caused the increased apoptosis of spermatogenic cells in BPA treated R. chensinensis [Acta Zoologica Sinica 54(5): 867–876, 2008].