title: Metabolic fate and disposition of [14C]hydroquinone given orally to Sprague-Dawley rats.
abstract: Hydroquinone (HQ) is used widely in industry and in commerce and is considered to have a low degree of toxicity. Although the metabolism of HQ has been studied elsewhere, a complete materials balance has not been reported. We investigated the metabolism of HQ in naive and HQ pretreated male Sprague-Dawley rats. [14C]HQ was administered by gavage in single doses of 5, 30, or 200 mg/kg to naive rats. HQ was given repeatedly by gavage to male rats at 200 mg/kg for 4 consecutive days followed by a single dose with 200 mg/kg of [14C]HQ. In separate studies rats were fed 5.6% unlabeled HQ in the diet for 2 days or were dosed by gavage with 311 mg/kg [14C]HQ. The excretion patterns of [14C]HQ and its metabolites were similar for rats dosed singly or repeatedly. Rats given a single dose of 200 mg/kg of [14C]HQ excreted 91.9% of the dose in the urine within 2-4 days; 3.8% was excreted in the feces, about 0.4% was excreted in expired air, and 1.2% remained in the carcass. Radioactivity was widely distributed throughout the tissues with higher concentrations in the liver and kidneys. A decrease in 14C tissue concentrations occurred from 48 to 96 h. The only radiolabeled compounds in the urine were HQ (1.1-8.6% of the dose), hydroquinone monosulfate (25-42%), and hydroquinone monoglucuronide (56-66%). Similar findings were observed for rats given HQ in the feed. There were no significant increases from controls for absolute or relative liver weights, liver microsomal protein concentrations, cytochrome b-5, cytochrome P-450 or cytochrome c reductase activity in rats dosed repeatedly with 200 mg/kg HQ. Cytochrome P-450 values were slightly but significantly decreased in rats dosed repeatedly with HQ compared with controls.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002250:Carbon Radioisotopes; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D005966:Glucuronidase / Q000494:pharmacology; D006873:Hydroquinones / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002250:Carbon Radioisotopes; D006873:Hydroquinones; D003577:Cytochrome P-450 Enzyme System; D005966:Glucuronidase; C031927:hydroquinone