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The urinary metabolic pattern of N-nitrosobutyl(4-hydroxybutyl)amine (NB4HBA) administered ip at a dose of 5 mg/kg body weight was studied in animals either pretreated with butylated hydroxyanisole (BHA) as a single oral dose of 50 or 250 mg/kg, or fed a diet containing 0.1 or 0.5% BHA. The 24-hr urinary excretion of NB4HBA, its glucuronic acid-conjugate (NB4HBA-G) and N-nitrosobutyl(3-carboxypropyl)amine (NB3CPA) in control rats were 0.12, 0.75 and 30% of the administered dose, respectively, and were not changed after a single oral dose of 50 mg BHA/kg. NB4HBA-G was significantly reduced in the urine of rats given 250 mg BHA/kg. In vitro assays carried out using rat-hepatic microsomal preparations as the source of the enzyme UDP-glucuronyl transferases (GT) and NB4HBA as the substrate, suggest that a competition between NB4HBA and BHA for the same enzyme may be the cause of the decreased NB4HBA-G excretion observed in vivo. A fourfold increase in NB4HBA-G urinary excretion was observed after chronic 0.5% BHA feeding; moreover, the glucuronic acid-conjugate of NB3CPA (NB3CPA-G), which was not detected in the controls or after acute BHA treatment, appeared in the urine of rats given dietary BHA for 3 wk, accounting for about 10% of the administered NB4HBA. In vitro experiments indicate that the increased glucuronides excretion may be the result of an elevated hepatic GT activity.

N-Nitrosodibutylamine and its omega-hydroxylated metabolite N-nitrosobutyl(4-hydroxybutyl)amine (NB4HBA) induce tumors in the urine bladder of different animal species through their common urinary metabolite N-nitrosobutyl(3-carboxypropyl)amine (NB3CPA), resulting from the oxidation of the alcoholic group of NB4HBA to a carboxylic group. NB4HBA disappearance from blood, the formation of its main metabolites, NB3CPA and NB4HBA-glucuronide (NB4HBA-G), and their urinary excretion, were investigated in rats after an i.v. dose of 1 mg/kg (5.7 mumol/kg). NB3CPA and NB4HBA-G formation was readily detectable 2 min after treatment and levels were still measurable at 120 and 30 min, respectively. The parent compound disappeared from blood 90 min after injection. The NB4HBA blood concentration-time profile was adequately described by a one-compartmental linear model. NB4HBA half-life was 8 min, total body clearance and renal clearance were 86.1 and 0.22 ml/min/kg, respectively. The 0-96-h urinary excretion of NB4HBA was 0.3% of the administered dose. NB3CPA half-life was 15 min; NB3CPA and NB4HBA-G urinary excretion were 36 and 11.7%, respectively, urinary excretion of known compounds accounting for less than 50%. After i.v. injection of NB3CPA equimolar to the NB4HBA dose, only 50% of unchanged compound was recovered in the urine and after NB4HBA-G, 41% of the administered dose was excreted unchanged, NB3CPA accounting for 10%. Thus NB3CPA and NB4HBA-G might undergo further biotransformation, suggesting that NB3CPA may not be the ultimate carcinogen responsible for urinary bladder tumor induction.