Correlation between the DNA damage in urinary bladder epithelium and the urinary 2-phenyl-1,4-benzoquinone levels from F344 rats fed sodium o-phenylphenate in the diet

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Abstract
The relationship between urinary metabolites and DNA damage in the urinary bladder epithelium of male and female rats was tested by alkaline elution assay after an intravesical injection of OPP or its urinary metabolites. 2-Phenyl-1,4-benzoquinone (PBQ) revealed a weak DNA-damaging activity in both sexes at 0.05–0.1%. OPP and phenyl hydroquinone (PHQ) had no effects at the same level. Histopathologically, a single intravesical injection of 0.1% PBQ induced epithelial hyperplasla of the bladder epitheliwn on day 5, but PHQ and OPP did nut induce it. Feeding studies with OPP-Na were also performed to examine the correlation between urinary PBQ levels and DNA damage in bladder epithelium. Slight DNA damage was observed in males given 1.0 and 2.0% OPP-Na in the diet for 3–5 months. The damage was dependent upon the dietary levels of OPP-Na. The amounts of OPP, PHQ and PBQ in urine were well correlated with the dietary levels of OPP-Na for male rats. The amounts of OPP, PHQ and PBQ were greater in male rats than in females given 2.0% OPP-Na diet for 5 months. The urinary pH of males was slightly higher than that of females. Since 0.4% sodIum bicarbonate did not cause DNA damage in the in-situ study, the urinary alkalinity may not affect the initiation steps of urinary carcinogenesis by OPP-Na. The present results indicate that the metabolite PBQ is the reactive species for the initiation steps of bladder tumors induced by OPP-Na and OPP.

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