Low-protein diet promotes sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N '-nitro-N-nitrosoguanidine in Wistar rats

Sodium chloride (NaCl) initiates and promotes experimental carcinogenesis i n rats. We recently found that a high-protein diet attenuates NaCl-enhanced gastric carcinogenesis in Wistar rats. To investigate the effect of a puri fied low-protein diet on NaCl-enhanced gastric carcinogenesis induced by N- methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats, rats were fed a p urified diet with an equalized caloric content containing 1% or 2% NaCl and 25% casein (normal-protein diet) or 10% casein (low-protein diet) after or al treatment with MNNG for 25 weeks. In week 52, neither 1% nor 2% NaCl had a significant effect on gastric carcinogenesis in rats fed a normal-protei n diet. However, oral administration of 2%, but not 1%, NaCl significantly increased the incidence of gastric cancers in rats fed a low-protein diet. Oral administration of 2% NaCl also significantly increased the bromodeoxyu ridine (BrdU)-labeling index and the ornithine decarboxylase (ODC) activity and decreased apoptosis of gastric cancers in rats fed a low-protein diet. However, 2% NaCl had no significant effect on these three parameters in ra ts fed a normal-protein diet. These findings indicate that a low-protein di et enhances the effect of NaCl in gastric carcinogenesis and that this enha ncement may be mediated by increased cell proliferation and reduced apoptos is of gastric cancers. (C) 1999 Elsevier Science Ireland Ltd. All rights re served.