The role of alkalizing and neutral potassium salts in urinary bladder carcinogenesis in rats

Using an initiation-promotion rat model, we have previouslyshown that the alkalizing salt KHCO₃ is a strong and the neutralsalt KCl a weak promoter of urinary bladder carcinogenesis.We have now studied the effects of these salts on rat urinarybladder epithelium without prior exposure to a bladder tumourinitiator. In four studies ranging in duration from 4 to 130weeks, (equimolar) amounts of K⁺ were administered in the dietto male and female rats (85 rats/sex/ group) as KHCO3 or KCl.Comparable increases in urinary volume and potassium levelswere found with both KHCO₃ and KCl, but only KHCO₃ induced anelevated urinary pH. The feeding of KHCO₃ resulted in simpleepithelial hyper-plasia and, after prolonged administration,in papillary/ nodular hyperplasia, papillomas and transitionalcell carcinomas of the urinary bladder. With KCl, only a slightincrease in proliferative urothelial lesions was found; onemale showed papillary hyperplasia and one female exhibited nodularhyperplasia and a papilloma. Our results allow the conclusionthat KHCO₃, a strong promoter of bladder carcinogenesis, iscapable of inducing urinary bladder cancer in rats without priorapplication of an initiator, whereas KCl, a weak tumour promoter,induced only a few (pre)neoplastic lesions.