The metabolic profile of sodium o-phenylphenate after subchronic oral administration to rats

We examined the metabolites of o-phenylphenol (OPP) in the urine of male and female rats dosed with 2% sodium o-phenylphenate (OPP-Na) in food from the age of 5 wk for 136 days. The urinary metabolites of OPP-Na produced during the 24 hr after OPP-Na feeding accounted for 55% of the dose in male rats and 40% in females. The main metabolites were OPP-glucuronide and 2,5-dihydroxybiphenyl (2,5-DHBP)-glucuronide. OPP metabolites in the free form accounted for only 1% of the total phenolic metabolites excreted. 2,5-DHBP was rapidly converted to the corresponding quinone in aqueous solvents but not in organic solvents. There was a clear sex difference in the proportions of urinary metabolites; the amount of 2,5-DHBP excreted by male rats in 24-hr urine was more than seven times that excreted by females. This result may be related to the finding that bladder tumours occur in male but not female rats fed OPP-Na in the diet.