DOSE-DEPENDENT PROMOTION EFFECTS OF POTASSIUM-CHLORIDE ON GLANDULAR STOMACH CARCINOGENESIS IN RATS AFTER INITIATION WITH N-METHYL-N'-NITRO-N-NITROSOGUANIDINE AND THE SYNERGISTIC INFLUENCE WITH SODIUM-CHLORIDE

The modifying effects of potassium chloride (KCl) ingestion on glandul ar stomach carcinogenesis were investigated in male Wistar rats induce d by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and were compared wit h those of sodium chloride (NaCl), A total of 120 male 6-week-old Wist ar rats were divided into six groups, each consisting of 20 animals, A fter initiation of treatment with a MNNG solution (100 parts/million) as their drinking water for 10 weeks, rats were fed a diet supplemente d with 5% NaCl, 2.5% NaCl, 2.5% NaCl plus 2.5% KCl, 5% KCl, 2.5% KCl, or a basal diet alone for the following 62 weeks. Under this experimen tal condition, there were no statistical differences in the final body weights between groups, The incidences of adenocarcinomas in the glan dular stomachs were significantly higher in the 5% NaCl and combined 2 .5% NaCl-plus-2.5% KCl groups (P < 0.05 and 0.01) than in the MNNG alo ne (control) group, The incidences of atypical or precancerous hyperpl asias in the glandular stomachs were increased significantly by the 5% NaCl, 2.5% NaCl-plus-2.5% KCI, and 5% KCL treatments (P < 0.05 or 0.0 1). The multiplicities of adenocarcinomas were significantly greater i n the 5% NaCl, 2.5% NaCl, and combined NaCl-plus-KCl groups (P < 0.05 or 0.01) compared with the control value, The multiplicity data for at ypical hyperplasias were most striking; namely, their multiplicities w ere increased significantly by the treatments of NaCl or KCI (P < 0.01 ) in a clear dose-dependent manner and enhanced synergistically by the combined treatment of NaCl and I(CI, Because the concentrations of KC I used in this study were about 1.3 times lower than those of NaCl on a molar basis, although the doses of each chemical were exactly the sa me on a weight-percent basis, it is suggested that the enhancing effec ts of KCI might not be much different from those of NaCl. The results in the present study thus indicate that, similarly to NaCl, KCI ingest ion exerts dose-dependent promoting effects and a synergistic influenc e with NaCl when given during the postinitiation phase of two-stage gl andular stomach carcinogenesis in rats.