Lack of Promoting Effect of Sodium Chlorate and Potassium Chlorate in Two-Stage Rat Renal Carcinogenesis

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Abstract
Sodium chlorate (NaClO3) and potassium chlorate (KClO3), which are byproducts of water disinfection with chlorine dioxide (ClO2), were tested for potential promoting effect in two-stage rat renal carcinogenesis. Three groups of 15 male F344 rats each were given N-ethyl-N-hydroxyethylnitrosamine (EHEN) at the level of 0.05% for the first 2 weeks during the initiation phase. Thereafter, the rats were treated orally for 25 weeks with NaClO3 (1%), KClO3 (1%), or distilled water (DW). Three other groups (controls) were treated similarly, except that DW was given in the initiation phase. All animals survived for the duration of the experiment. Renal neoplastic lesions were classified histologically as dysplastic foci (DF) and renal cell tumors (RCT). The number of these lesions per unit area, in six sections from each kidney, was determined microscopically. There were no statistically significant differences in the incidences and in the mean number of DF and RCT of the kidney between compound-and DW-treated rats initiated with EHEN. It is concluded that NaClO3 and KClO3 show no promoting effect in rat renal carcinogenesis under the conditions of this study.