Dose-dependent promoting effects of sodium chloride (NaCl) on rat glandular stomach carcinogenesis initiated with N-methyl-N'-nitro-N-nitrosoguanidine.

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.