Comparison of the responses of male rats to dietary sodium saccharin exposure initiated during nursing with responses to exposure initiated at weaning.

In an attempt to define the role of exposure to sodium saccharin (NaS) during early life on the subsequent development of bladder tumours, we compared the responses of male rat pups to exposure to 5% dietary NaS initiated at parturition with those to exposure initiated at weaning. We also compared the effects of exposure from parturition to NaS given in a low-carbohydrate (L-CHO) diet with those of NaS in rat chow. NaS ingestion by the dam was associated with low saccharin concentrations in the pups' urine and had no effect on the caecal or bladder mass in the suckling pups. In the 10 wk after weaning, the rats ingesting NaS in chow showed decreased weight gain and increases in feed consumption, mass of caecal contents and tissue, urine output, bladder mass, relative water consumption (g water consumed/g feed consumed) and bladder hyperplasia. Except for bladder hyperplasia these effects were generally greater in the rats exposed to NaS from parturition than in those exposed only from weaning. The animals exposed to NaS in the L-CHO diet had the highest level of urinary saccharin but showed no bladder hyperplasia. The significance of these findings to the role of pre-weaning saccharin exposure in bladder tumorigenesis is discussed, and it is concluded that the effects on urinary parameters and the bladders of rats exposed to NaS during suckling and weaning may be secondary to the effects of NaS on the gastro-intestinal tract.