Metabolic fate of N-butyl-N-(4-hydroxybutyl)nitrosamine in the rat.

The metabolic fate of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was studied in the rat, to investigate the possibility of a relationship between urinary metabolites and organotropic carcinogenicity to the urinary bladder of this N-nitrosamine. The principal urinary metabolite of BBN was identified as N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN). Several minor metabolites characterized were transformation products of BCPN formed by beta-oxidation according to the Knoop mechanism, i.e., N-butyl-N-(2-hydroxy-3-carboxy-propyl)nitrosamine, N-butyl-N-(carboxymethyl)nitrosamine and N-butyl-N-(2-oxopropyl)nitrosamine; glucuronic acid conjugates of BBN and BCPN were also detected. No BBN was detected in the urine. A possible correlation of the urinary excretion of BCPN with selective induction of bladder tumors by BBN in rats is discussed in relation to the carcinogenic action of BCPN.