The significance of nucleolar organizer regions in bladder epithelial lesions induced by N-butyl-N-(4-hydroxybutyl)nitrosamine in rat

Park, Kyoung Jun; Yoon, Jai Young

Abstract

It is known that the activity of tumor cells correlates with the malignant potential of tumors. Nucleolar organizer regions(NORs) are loops of DNA which occur in nucleoli and which possess ribosomal DNA genes. Ribosomal DNA genes transcribe to ribosomal RNA by RNA polymerase I and are of vital significance in the ultimate synthesis of protein. Proteins associated with the NORs are stained with silver nitrate(Ag-NORs). Ag-NORs were studied in various tumors and might reflect the activity of cells and might be and indicator of the degree of malignancy in tumors. 0.05 % N-Butyl-N(4-hydroxybutyl) nitrosamine(BBN) in drinking water was given for 8 and 14 weeks to induce pre-neoplastic and neoplastic vesical epithelial lesions in female Wister rats. Ag-NORs were stained by the simple one-step silver colloid staining in routine processed, formalin-fixed paraffin sections of bladder lesions induced by N-butyl-N(4-hydroxybutyl) nitrosamine(BBN) in rat. The mean number of silver stained NORs(Ag-NORs) was as follows : normal transitional epithelium was 1.64+/-0.25(mean+/-SD; n=10), simple hyperplasia was 2.24+/-0.24(n=7). nodular hyperplasia was 2.63+/-0.12 (n=6), transitional cell papilloma was 3.24+/-0.28(n=6) and transitional cell carcinoma was 4.52+/-0.32(n=10). Based on the above results, we concluded that the mean number of Ag-NORs showed a stepwise increase from normal transitional epithelium through simple hyperplasia and nodular hyperplasia to papilloma and carcinoma of bladder epithelium induced by BBN in rat and may reflect proliferative activity of cells. Further investigations may be needed to confirm whether the number or quantification of Ag-NORs is a useful method for evaluating proliferative activity of neoplastic lesions or another indicator of prognosis in human bladder cancer.