Search

Species variations in response to urinary bladder carcinogens, N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), N-ethyl-N-(4-hydroxybutyl)nitrosamine (EHBN), and N,N-dibutylnitrosamine (DBN), were investigated in several animal species from the metabolic point of view. Since N-butyl-N-(3-carboxypropyl) nitrosamine (BCPN) and N-ethyl-N-(3-carboxypropyl) nitrosamine (ECPN) had been found to be the principal urinary metabolites which are responsible for the induction of bladder tumors by BBN or DBN and EHBN, respectively, in rats, acidic urinary metabolites with the N-nitroso moiety were isolated and determined by a colorimetric method after oral administration of these nitrosamines to rats, mice, hamsters, guinea pigs, and dogs. Qualitatively almost no species differences were observed among these animals in regard to the urinary metabolites except in the case of mice, in which the glycine conjugate of BCPN was isolated from the urine and identified as the principal metabolite of BBN and DBN. However, appreciable quantitative differences in the urinary excretion of BCPN or ECPN were found among these animal species, indicating that the differences in the susceptibilities of different animal species to urinary bladder carcinogenesis induced by BBN, DBN and EHBN may be closely related to the different extents of urinary excretion of the active metabolites of these nitrosamines.

The metabolic fate of two urinary bladder carcinogens, N-butyl-N-(4-hydroxy-butyl) nitrosamine (BBN) and N-N-dibutylnitrosamine (DBN), was studied in the guinea pig, in order to elucidate species differences of response to these N-nitrosamines in this animal species and the rat. Based on the urinary metabolites characterized after oral administration of these compounds, the metabolic pathways of BBN and DBN in the guinea pig were shown to be essentially similar to those in the rat. The principal urinary metabolite of BBN and DBN in the guinea pig, however, was not N-butyl-N-(3-carboxypropyl) nitrosamine (BCPN), as was the case in the rat, but the glucuronic acid conjugate of BBN and that of N-butyl-N-(3-hydroxybutyl) nitrosamine, respectively. The species variation in response to BBN and DBN as bladder carcinogens in these animals is discussed on the basis of the urinary excretion of BCPN.

The metabolic fate and carcinogenicity fo three omega-hydroxy derivatives of N-alkyl-N-(4-hydroxybutyl) nitrosamines, potent bladder carcinogens, were investigated in the rat. They were N-(2-hydroxyethyl)-N-(4-hydroxybutyl)-nitrosamine (HEHBN), N-(3-hydroxypropyl)-N-(4-hydroxybutyl) nitrosamine (HPHBN), and N-N-bis(4-hydroxybutyl) nitrosamine (BHBN). The principal urinary metabolite of HEHBN as well as HPHBN was identified as the corresponding 3-carboxypropyl compound, while the main metabolite of BHBN was N,N-bis (3-carboxypropyl) nitrosamine, indicating the preferential metabolic oxidation of the 4-hydroxybutyl chain to the 3-carboxypropyl group in the N-(omega-hydroxyalkyl)-N-(4-hydroxybutyl) nitrosamines. All three N-nitrosamines having the 4-hydroxybutyl chain induced neither bladder tumor nor any tumor in other organs under conditions similar to those used for N-alkyl-N-(4-hydroxy-butyl) nitrosamines. The essential structural and metabolic requirements in N-nitrosamines for the induction of bladder cancer in the rat are discussed.