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The excretion of nitrate, nitrite, apparent total N‐nitroso compounds and volatile nitrosamines was measured in 24 hr urine from 61 Egyptians, divided into 4 groups: controls, Schistosoma haematobium‐infected patients and bladder cancer patients with and without a history of schistosomal infection. Urinary nitrate in S. haematobium‐infected patients was significantly higher than in the other 3 groups. Nitrite was below the detection limit of the method (≤0.015 μg/mg creatinine) in all but one of the control samples. S. haematobium infection significantly increased urinary nitrite to 0.9 ± 1.16 μg/mg creatinine (mean ± SD, p = 0.001). In both bladder cancer groups, nitrite was about 20 times that in S. haematobium‐infected patients without bladder cancer. Excretion of apparent total N‐nitroso compounds paralleled that of nitrite. Overall, a good correlation was observed between these 2 variables (r = 0.71, p = 0.0001). N‐nitrosodimethylamine was present in all the samples analyzed. S. haematobium infection significantly increased urinary N‐nitrosodimethylamine level compared with that of controls (4.02 ± 1.61 and 2.04 ± 2.97 ng/mg creatinine, respectively, p = 0.01). Among cancer patients, N‐nitrosodimethylamine was higher than in controls only in those with schistosomal infection. The presence of N‐nitroso compounds and N‐nitrosodimethylamine in the urine of S. haematobium‐infected patients both before and after the development of cancer, and the observation that these compounds also occur in bladder cancer patients with no history of schistosomal infection, suggest that these compounds might have a role not only in the initiation of the carcinogenic process, but also in its progression. Int. J. Cancer 82:789–794, 1999. © 1999 Wiley‐Liss, Inc.

The present work is an up-to-date approach to study the correlation between the excretion pattern of tryptophan metabolites along the kynurenine pathway (after loading with 2 gm. L-tryptophan), and the N-nitrosamine content in urine of bilharzial bladder cancer patients. The control group was composed of healthy subjects who had no reported history of S. haematobium infection and no current bacterial cystitis. The N-nitrosamine content was determined by the colorimetric method of Eisebrand and Preussmann (1970). It was demonstrated that 64 per cent of the patients metabolized the tryptophan load abnormally and the others metabolized it almost normally. Moreover, the N-nitrosamines were present in 43 per cent of controls and 93 per cent of patients have these derivatives in higher values. The presence of an inverse correlation between certain tryptophan metabolites, shown previously to be bladder carcinogens, and the N-nitrosamine content, especially after loading, was interpreted in view of the possible conversion of some tryptophan metabolites into N-nitrosamines either under endovesical conditions or during the execution of the colorimetric determination of these compounds. Therefore, thorough investigation is urgently needed to study the origin of these urinary N-nitrosamines. Moreover, improved method(s) for their colorimetric determination are also urgently needed.

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