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Urinary excretion of N ‐nitrosamino acids and nitrate by inhabitants of high‐ and low‐risk areas for stomach cancer in Poland
Author(s) -
Zatonski W.,
Ohshima H.,
Przewozniak K.,
Drosik K.,
Mierzwinska J.,
Krygier M.,
Chmielarczyk W.,
Bartsch H.
Publication year - 1989
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910440513
Subject(s) - nitrosation , ingestion , urine , nitrosamine , excretion , chemistry , proline , nitrate , urinary system , calorie , medicine , food science , endocrinology , physiology , zoology , biochemistry , amino acid , carcinogen , biology , organic chemistry
Urine samples were collected from 96 inhabitants of a high‐risk rural area and a low‐risk urban area for stomach cancer in Poland, according to the following protocol: (1) when they were undosed; (2) after ingestion of proline 3 times a day; and (3) after ingestion of proline together with vitamin C 3 times a day. The samples were analyzed for N ‐nitrosamino acids and nitrates, as indices of exposure to preformed and endog‐enously formed N ‐nitrosamines. The median values of N ‐nitrosoproline (NPRO) and N ‐nitrosothiazolidine 4‐carboxylic acid (NTCA) excreted in the urine of undosed subjects were not different between the two areas; but N ‐nitrososarcosine and 3‐( N ‐nitroso‐ N ‐methylamino)propionic acid levels were 3‐ to 4‐fold higher in subjects of the high‐risk area. After intake of proline, the NPRO level increased ( p < 0.02) only in subjects in the high‐risk area; intake of vitamin C tended to inhibit this increase in NPRO and lowered the levels of other nitrosamino acids. The urinary level of nitrates was 1.4‐fold, but significantly higher among subjects in the high‐risk area than among those in the low‐risk area; nitrate levels were not correlated with the amounts of cured meat or types of vegetables consumed. Urinary nitrate levels and excretion of NPRO, NTCA and the sum of all nitrosamino acids analyzed showed positive, though modest, correlations. These results indicate a higher potential for endogenous nitrosamine formation, possibly by intragastric nitrosation among subjects in the high‐risk rural area.