Over-expression of apoptosis-related proteins contributes to muscular damage in the obstructed ureter of the rat

Objective To determine the role of apoptosis-related proteins (Myc, Bax, Bcl-2, and Bcl-X-L) in muscular damage in obstructed rat ureters. Materials and methods The in situ end-labelling of DNA fragments and the expression of apoptosis-related proteins were assessed, using immunohistochemistry. in 54 female Sprague-Dawley rats in which unilateral ureteric obstruction was caused by ureteric ligation. Results The severity of ureteric damage increased during the period of obstruction. Apoptotic cells and the expression of Bax were detected in the smooth muscle layer from 14 days after ligation. The percentage of apoptotic cells and the expression of Bax in the smooth muscle layer increased and reached a peak 21 days after ligation. and then declined. The expression of Myc was also detected in the smooth muscle layer 14 days after ligation but reached a peak at 28 days. The expressions of Bcl-2 and Bcl-X-L in the smooth muscle layer were only detected 21 and 28 days after ligation. The numbers of apoptotic cells in the smooth muscle layer correlated significantly with the expressions of Myc and Bax (r=0.7360 and 0.7432, respectively: both P<0.005), and with the expression index of Bax/Bcl-2 and Bax/Bcl-X-L, (r=0.8909 and 0.8592, respectively: both P<0.001). Conclusions Apoptosis-related proteins might be important in regulating cell apoptosis in ureteric damage during the development of obstructive uropathy.