Promoting effect of sodium chloride in 2-stage urinary bladder carcinogenesis in rats initiated by N-butyl-N-(4-hydroxybutyl)nitrosamine.

The promoting effect of sodium chloride (NaCl) in 2-stage urinary bladder carcinogenesis in F344 rats initiated by 2 doses of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) was investigated. The incidences of PN hyperplasia were significantly higher in rats initiated with 0.01 or 0.05% BBN when they were given diet containing 10% NaCl for 32 weeks than when they were given control diet. The incidence of papilloma in rats given 0.05% BBN followed by diet containing 10% or 5% NaCl tended to be higher than that in control rats. The urine of rats given diet containing NaCl was larger in volume and had lower osmolality than that of controls. The total urinary sodium and chloride contents were also increased, whereas those of potassium and phosphorus were decreased. No calculus formation or crystalluria was observed. These data suggest that excess intake of sodium as NaCl has a weak promoting effect in 2-stage urinary bladder carcinogenesis.