Effects of NaCl, Tween 60 and a low dose of N-ethyl-N'-nitro-N-nitrosoguanidine on gastric carcinogenesis of rat given a single dose of N-methyl-N'-nitro-N-nitrosoguanidine.

Effects of NaCl, Tween 60 and N-ethyl-N'-nitro-N-nitroso-guanidine (ENNG) on gastric carcinogenesis were investigated in male Wistar rats. Animals received a single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at 250 mg/kg body weight by gastric tube followed one week later by either 10% NaCl in their diet, twice-weekly applications of 1 ml of saturated NaCl solution by gastric tube, 1.0% Tween 60 in their drinking water or 0.0005% ENNG in their drinking water. One group of rats were given MNNG 24 h after a single application of 1 ml of saturated NaCl solution to investigate the effect of NaCl on initiation. A single dose of MNNG to rats resulted in development of multiple epithelial tumors in the forestomach and no epithelial tumors in the glandular stomach after 52 weeks. There were no differences in tumor incidences of the forestomach and glandular stomach between experimental groups which were given a subsequent treatment with NaCl or Tween 60 and the control group with MNNG alone. ENNG significantly enhanced the tumor induction in the glandular stomach, while ENNG alone did not induce any tumors in the stomach. The NaCl treatment prior to MNNG administration also increased tumor development in the glandular stomach but not in the forestomach.