Effect of dietary carbohydrate type and content on the response of male rats to dietary sodium saccharin

The toxicity of purified cellulose in studies with laboratory animals

The available literature has been reviewed for studies in laboratory animals using purified cellulose, as the production of purified cellulose may result in trace organochlorine contamination. The chronic ingestion of purified cellulose over the entire lifespans in rats and mice does not result in any increase in spontaneous disease or neoplasia. Further, purified cellulose does not display promotional activity in the mammary gland, the colon, or the bladder of rats and does not significantly alter the absorption or the metabolism of dietary components. No adverse effects were found on reproduction or neonate development in rats and mice. Therefore, no adverse health effects in humans are expected from exposure to purified cellulose.

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.

Inhibition of the serosal sugar carrier in isolated intestinal epithelial cells by saccharin

Isolated intestinal cells accumulate certain monosaccharides via an Na+-dependent, active transport system localized in the brush-border membrane, and release sugar molecules at the basolateral boundary via a facilitated diffusion, passive system. Work described here indicates that sodium saccharin (25-130 mM) has little if any direct effect on the active transport system, but that the passive transport system is inhibited by saccharin. A short period of exposure (10-60 min) is required for expression of the effect, which is detectable at saccharin concentrations as low as 10 mM. At 100 mM-sodium saccharin, as much as 50% inhibition occurs. Saccharin also appears to act as a weak metabolic inhibitor. The basis of the 'non-specific' effect is not understood, but it can compromise the capacity of the epithelial cells to form sugar gradients. When a sugar is accumulated that satisfies both transport systems (for example 3-O-methylglucose) the effect of saccharin on the passive transport system is the predominant one, and the cells establish a higher sugar gradient than that observed in the absence of saccharin. The 'non-specific' metabolic effect is manifested as an inhibition of sugar gradient formation when sugars that satisfy only the active system (such as alpha-methylglucoside) are accumulated.