Although aromatic amines are widely used as raw materials for dyes, some of them have been concerned about carcinogenicity in the urinary bladder. We examined early changes in histopathology and the formation of γ-H2AX, a biomarker of DNA damage, in the urinary bladder of rats to investigate the mechanisms of mucosal damage induced by monocyclic aromatic amines. 6-week-old male F344 rats were administered 0.4% or 0.8% o-toluidine, 0.3% or 1.0% o-anisidine, 0.4% 2,4-xylidine, 0.2% p-toluidine, or 0.6% aniline in the diet for 4 weeks. Animals were sequentially killed from day 2 to after 2 weeks of recovery, and histopathological and immunohistochemical analyses were performed. In the 0.8% o-toluidine group, there was sequential progression of bladder lesions, characterized by edematous changes and intramucosal hemorrhage at day 2 and formation of granulation tissue with mononuclear cell infiltration at week 1, followed by diffuse hyperplasia at weeks 2 and 4. In the 1.0% o-anisidine group, simple hyperplasia only with slight inflammation was detected from week 1. Whereas γ-H2AX-positive bladder epithelial cells in the 1.0% o-anisidine group were significantly increased in a time-dependent manner, transient increases in γ-H2AX-positive cells were detected at day 2 and week 1 in the 0.8% o-toluidine group. No apparent bladder lesions or increases in γ-H2AX formation were observed in any other groups. These results revealed different mechanisms of bladder mucosal damage associated with o-toluidine and o-anisidine. Moreover, immunohistochemical analysis for γ-H2AX suggested that both compounds may induce DNA damage in epithelial cells, mainly basal cells, of the bladder mucosa.
Aromatic amine γ-H2AX o-Anisidine o-Toluidine Rat Urinary bladder
This is a preview of subscription content, log in to check access.
This work was supported by a Health and Labour Sciences Research Grant for the Research on Risk of Chemical Substances from the Ministry of Health, Labour and Welfare, Japan. The authors thank Ayako Saikawa and Yoshimi Komatsu for expert technical assistance in processing histological materials.
Compliance with ethical standards
Conflict of interest
Takanori Yamada is an employee of Sanwa Kagaku Kenkyusho, Nagoya, Japan. All authors declare that they have no conflict of interest.
Koss LG, Lavin P (1970) Effects of a single dose of cyclophosphamide on various organs in the rat. II. Response of urinary bladder epithelium according to strain and sex. J Natl Cancer Inst 44(5):1195–1200Google Scholar
Thompson CZ, Hill LE, Epp JK, Probst GS (1983) The induction of bacterial mutation and hepatocyte unscheduled DNA synthesis by monosubstituted anilines. Environ Mutagen 5(6):803–811CrossRefGoogle Scholar
Vasconcelos-Nobrega C, Colaco A, Lopes C, Oliveira PA (2012) BBN as an urothelial carcinogen. In Vivo 26(4):727–739Google Scholar
Ward E, Carpenter A, Markowitz S, Roberts D, Halperin W (1991) Excess number of bladder cancers in workers exposed to ortho-toluidine and aniline. J Natl Cancer Inst 83(7):501–506CrossRefGoogle Scholar
Weisburger EK, Russfield AB, Homburger F et al (1978) Testing of twenty-one environmental aromatic amines or derivatives for long-term toxicity or carcinogenicity. J Environ Pathol Toxicol 2(2):325–356Google Scholar