EFFECT OF 2-CHLORO-4-METHYLTHIOBUTANOIC ACID IN A RAPID BIOASSAY FOR GASTRIC CARCINOGENS

2-Chloro-4-methylthiobutanoic acid (CMBA, a mutagen from Japanese salt ed fish) at 15-500 mg/kg body weight induced several-fold increase in replicative DNA synthesis (RDS) (P < 0.05) after 80 min and 17 h, equi vocal unscheduled DNA synthesis (UDS) after 80 min and necrosis 80 min after its administration in the stomach pyloric mucosa of F344 and AC I male rats. A positive control, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 50 mg/kg body weight), induced RDS, UDS and erosion. However, t he negative control L-methionine (500 mg/kg body weight) did not displ ay any effect. The results suggest possible tumor-initiating and -prom oting activity of CMBA but at a lower potency than that of MNNG.