Abstract
[Background] The short-term bioassays for detection of carcinogenicity are expected for rapid and efficient safety evaluation of chemicals and improvement of animal welfare. We have performed immunohistochemistry forγ-H2AX, known as a biomarker of DNA damage, in the kidney of rats to develop a novel method for early detection of renal carcinogens.
[Methods] Six-week-old male F344 rats were orally treated with renal carcinogens, such as hexachlorobutadiene (HCBD), 1-amino-2,4-dibromoanthraquinone (ADBAQ), dimethylnitrosamine (DMN), N-ethyl-N-hydroxyethylnitrosamine (EHEN), and azoxymethane (AOM), for 28 days, and immunohistochemistry forγ-H2AX was performed. We also examined the dose dependency ofγ-H2AX formation in the kidney of rats using multiple doses of genotoxic (tris(2,3-dibromopropyl) phosphate; TBPP) and nongenotoxic (d-limonene; LIM) renal carcinogens for 28 days.
[Results and Discussion] The ratios ofγ-H2AX-positive cells in tubular epithelial cells in the all five groups were significantly increased in both the cortex and outer stripe of the outer medulla compared to the control group. In addition, γ-H2AX formation in the TBPP and LIM-treated groups showed a distinct dose correlation, regardless of the presence of genotoxicity. Thirteen of fourteen renal carcinogens examined so far increased γ-H2AX formation in the kidney, whereas all of seven non-renal carcinogens showed the same level as the control group. These results suggest thatγ-H2AX immunostaining can detect renal carcinogenicity of chemicals in a short-term test with high sensitivity and specificity.
