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A simple and sensitive procedure is described for the quantitative determination of N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), the principal metabolite of the bladder carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN-4), in urine. BCPN was analyzed by gas-liquid chromatography as its methyl ester after extraction with ethyl acetate from urine followed by esterification with diazomethane. Species and strain variations in susceptibility to bladder carcinogenesis induced by BHBN-4 are discussed in relation to the urinary excretions of BCPN, determined by the new procedure, after oral administration of the compound to rats (4 strains), mice, hamsters, and guinea pigs at a dose approximately equal to the daily dose used in chronic carcinogenicity assay.

The metabolic fate of N, N-dipropylnitrosamine (DPN) and N, N-dipentyl-(=diamyl) nitrosamine (DAN), which induced tumors principally in the liver and esophagus but not in the urinary bladder, was studied in the rat, in order to elucidate the reason for this lack of carcinogenicity to the urinary bladder in contrast with the butyl homolog, N, N-dibutylnitrosamine (DBN), a potent bladder carcinogen. The principal urinary metabolite of DPN was identified as the omega-oxidation product N-propyl-N-(2-carboxyethyl) nitrosamine. The (omega-1)-oxidation product N-propyl-N-(2-hydroxypropyl) nitrosamine and its glucuronic acid conjugate were also characterized as metabolites. The principal urinary metabolite of DAN was N-amyl-N-(2-carboxyethyl) nitrosamine, which was formed by metabolic shortening of the amyl chain by omega- and beta-oxidations according to the Knoop mechanism. Besides this, seven compounds oxidized at omega-, (omega-1)-, (omega-2)-, and (omega-3)- positions of one or both amyl chains were isolated and characterized, some of which were shown to be also present as the corresponding glucuronide. The metabolic pattern of DPN and DAN was compared with that of DBN, and the lack of carcinogenicity of the former N-nitrosamines to the urinary bladder of rats is discussed on the basis of their urinary metabolites.

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.

We assessed the possibility to detect promoters of bladder carcinogenesis by a short-term in vitro assay utilizing the activation of Epstein-Barr virus (EBV) expression in EBV genome-carrying human lymphoblastoid cells. This system is composed of EBV-nonproducer Raji cells as the indicator, n-butyrate as the EBV-inducer and the test substance. None of eight known bladder carcinogens (2-naphthylamine, 2-acetylaminofluorene, N-butyl-N-(4-hydroxybutyl)nitrosamine, N-butyl-N-(3-carboxypropyl) nitrosamine, N-methyl-N-nitrosourea, N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide, benzidine, cyclophosphamide) or five promoters (sodium saccharin, sodium cyclamate, urea, allopurinol, DL-tryptophan) were detected by this system. Normal urine from 20 rats did not activate the EBV genome. Neither the 0.45 micron membrane filtrates nor ether extracts of urine obtained from rats given one of 4 bladder carcinogens, 4 promoters or phorbol 12-myristate 13-acetate reacted with this system, whereas those from rats given either vincristine or vinblastine did, although their activity for promoting bladder carcinogenesis is not known. Urine samples from 42 patients with bladder cancers, when tested as filtrates, ether extracts or XAD-2 resin adsorbates, did not activate EBV expression. These results suggest that EBV-activating substances contribute little to promotion of bladder carcinogenesis and that this test might not be applicable for screening of tumor promoters in urine.