The influence of different doses of
sodium chloride (NaCl) on glandular stomach
carcinogenesis was examined in male outbred Wistar rats after initiation with
N-methyl-N'-nitro-N-nitrosoguanidine (
MNNG). Rats were given 100 p.p.m.
MNNG in their
drinking water for 8 weeks and then fed a diet supplemented with NaCl at doses of 10, 5, 2.5 or 0% for the next 82 weeks. The administration of 10% and 5% NaCl significantly enhanced the development of gastric
adenocarcinomas and
adenomas in a dose-dependent manner. Similar but non-significant tendencies for increase were also seen in the group given 2.5% NaCl compared to the
MNNG-alone group values. Clear linear correlations between incidences of
adenocarcinomas and/or
adenomas and the concentration of supplemented NaCl were found. Mesenchymal
tumors were also induced in the stomach of rats given
MNNG, although the incidence was not statistically different between groups. Independent of the
MNNG treatment, urinary lipid peroxidation levels were significantly increased in the NaCl-treated groups as compared to the control values. Thus, the results in the present study indicate that NaCl exerts dose-dependent
tumor promoting activity on gastric
carcinogenesis in rats, even at doses as low as 2.5%, when given after
MNNG initiation.