The role of urinary pH and sodium ion concentration in the promotion stage of two-stage carcinogenesis of the rat urinary bladder

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Abstract
The promoting activities of NaHCO 3 and NaCl in two-stage urinary bladder carcinogenesis in rats initiated with N -butyl N -(4-hydroxybutyl)nitrosamine (BBN) were investigated. Male F344 rats were given 0.05% BBN in their drinking water for 4 weeks and then treated with basal diet containing either 3% NaHCO 3 , 1% NaCl or no added chemical for 32 weeks. NaHCO 3 significantly increased the induction of neoplastic and preneoplastic lesions of the urinary bladder, whereas NaCl did not. NaHCO 3 produced elevation of urinary pH and urinary Na + concentration. NaCl increased urinary Na + concentration without the elevation of urinary pH. In an additional experiment, DNA synthesis in the urinary bladder epithelium was significantly increased in the groups given 3% NaHCO 3 , 5% sodium L-ascorbate and 1% NaCl. These results confirm that urinary components, increase in urinary pH and Na + concentration play an important role in the promotion of urinary bladder carcinogenesis in rats