Effect of inherent urine output on the response of male rats to 7.5% dietary sodium saccharin

Young male rats were preselected as high urine (57 g/kg body weight) or low urine (35 g/kg) voiders and were fed a diet containing 7.5% sodium saccharin (NaS) for 10 wk. Urine output was found to be a stable characteristic and high urine output was associated with increased water and feed consumption and increased weight gain. Rats responded in a very similar fashion to 7.5% dietary NaS regardless of their inherent urine output. NaS ingestion was associated with increases in water consumption, caecal mass and urine volume. Among rats that had ingested 7.5% dietary NaS for 10 wk there was a high incidence (12/20) of bladder epithelial hyperplasia. The results are discussed with regard to the concept that increased urine output is an important factor in NaS-induced bladder tumours.