Saccharin metabolism and tumorigenicity.

Exposure of male Charles River CDI rats to a 5% saccharin diet in utero and throughout weaning, conditions associated with tumor induction, did not induce detectable metabolism (less than 0.4% of the oral dose) of tritiated saccharin in vivo. No metabolites (less than 0.06 microgram per kilogram per 24 hours) were detected in the urine of normal rats given a tracer dose. Pretreatment with 3-methylcholanthrene did not induce saccharin metabolism.

Saccharin and other sweeteners: mutagenic properties.

Saccharin preparations commonly distributed as artificial sweeteners exhibited mutagenic activity in bacterial tests. When administered orally to mice, mutagenic activity was demonstrable in the urines of these animals as well as in a host-mediated assay. Highly purified saccharin was not mutagenic in the direct assay, but the urines of mice to which this material had been administered exhibited mutagenic effects on one tester strain (Salmonella typhimurium TA100). Two other sweeteners, neohesperidin dihydrochalcone and xylitol, had no detectable mutagenic activity in any of these assays using his- Salmonella typhimurium strains TA100 or TA98.

The effect of different salts of saccharin on the rat urinary bladder.

Weanling male F344 rats were fed the sodium, potassium, or calcium salt of saccharin or acid saccharin as 5% of the diet by weight for 10 weeks. Sodium saccharin induced significant urinary bladder epithelial proliferation as determined by the labelling index following [3H]thymidine incorporation and by light and scanning electron microscopic evaluation. Potassium saccharin also significantly increased the labelling index but less than the sodium salt. Calcium saccharin and acid saccharin did not significantly increase the labelling index. Similar differences were evident by light and scanning electron microscopy. These differences were not due to differences in the level of saccharin excretion in the urine following feeding of the various salts. Differences in urinary pH and urinary concentration of sodium and calcium were observed between rats fed the various forms of saccharin.

The metabolism of saccharin in animals.

Rats given oral doses of [3-14C] saccharin excreted 56-87% of the labeled dose in the urine and 10-40% in the feces during 7 days. Distribution studies showed that the highest levels of 14C were in the kidneys and bladders. The bile was not a significant route of excretion. The presence of labeled CO2 in expired air indicated that saccharin was decarbosylated to a slight degree. DEAE chromatographic separation and isolation of labeled compounds from urine samples showed that more than 99% of the urinary 14C was unchanged saccharin. Up to 1.0% of the 14C was a metabolite identified as 0-sulfamoylbenzoic acid. Comparative metabolic profiles of a dog, rabbit, guinea pig and hamster indicated that there was little difference in the pattern due to animal species or dose level.

Determination of sodium saccharin in animal feed, wastewater and human urine by high-pressure liquid chromatography.

Analytical methods are described for sodium saccharin in animal feed, wastewater and human urine at levels as low as 10, 0.1 and 10 ppm, respectively. Samples of animal feed and wastewater are subjected to liquid-liquid partitioning then the feed is further cleaned up on a column of silica gel prior to analysis by high-pressure liquid chromatography (HPLC) using a paired-ion mobile phase and an ultraviolet detector set at 230 nm. Samples of human urine require a cleanpu on a column of XAD-2 prior to the partitioning and silica gel steps as well as an adjustment in the composition of the mobile phase to quantify saccharin. Data concerning partition values and the stability of sodium saccharin in animal feed are also presented.

The urinary excretion of bacterial amino-acid metabolites by rats fed saccharin in the diet.

Administration of a diet containing 7.5% saccharin to adult male rats for 40 days caused a three- to four-fold increase in the daily excretion of indican and rho-cresol. Indican is formed from indole which is a microbial metabolite of tryptophan, whilst rho-cresol is formed by the gut flora from tyrosine. The excretion of phenol, which is also a microbial metabolite of tyrosine, was abolished by saccharin administration for 40 days. Analysis of urines collected at 13, 18 and 24 months during a two-generation cancer bioassay showed that these changes occur throughout the life of saccharin-treated rats. These data indicate that saccharin changes the metabolism of amino acids by the gut flora, leading to an increased formation of products known to have promoting or co-carcinogenic properties.

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

The role of dietary carbohydrate composition and concentration in the response of male rats to sodium saccharin (NaS) was ascertained by comparing the response to 5% dietary NaS in rats given diets containing 65% starch, 50% sucrose together with 15% starch, 65% glucose, or 3% sucrose. NaS induced similar levels of caecal enlargement and increases in urine volume and bladder mass when given with any of the three forms of carbohydrate at 65% in the diet. However with the 3% sucrose diet, NaS caused a lesser caecal enlargement and no increase in urine volume or bladder mass. These findings suggest that NaS not only inhibits saccharide hydrolysis but also inhibits glucose transport. The significance of these findings in relation to NaS-associated bladder tumours is discussed.

[Mutagenicity of urine after ingestion of saccharin in man]. / Mutagénicité des urines après ingestion de saccharine chez l'homme.

In vitro tests of mutagenicity help detect carcinogenic substances. A variation of the Ames test may be used to study the mutagenicity of urine after exposition of the organism in vivo. Saccharin is a widely used artificial sweetener excreted in the urine which can induce dose-dependent tumours of the bladder in the animal. We studied the mutagenicity of the urine of healthy volunteers after the ingestion of a single dose of saccharin. The results show a mutagenic effect related to the dose ingested in two types of Salmonella typhimurium (TA 98 and TA 38). These results are difficult to interpret as saccharin is not mutagenic in vitro alone or in the presence of control urine which eliminates a direct carcinogenic or cocarcinogenic effect; we were unable to detect impurities or metabolites. This study underlines the difficulty of prophylactic detection of chemical carcinogens.

The fate of saccharin impurities: the excretion and metabolism of [3-14C]Benz[d]-isothiazoline-1,1-dioxide (BIT) in man and rat.

1. The 14C label of [3-14C]benz[d]isothiazoline-1,1-dioxide (BIT) (40 mg/kg) was rapidly eliminated (97% dose in 24 h), largely in the urine (92% dose in 24 h), after oral administration to rats. Larger doses (400 mg/kg) were eliminated more slowly after oral or parenteral administration (45--60% within 24 h) mostly in the urine (42--53%). Little 14C (2--3% dose) was present in the faeces after intraperitoneal (400 mg/kg) or low oral (40 mg/kg) doses, but the presence of larger amounts (12% dose) after larger oral doses (400 mg/kg) indicated incomplete absorption. 2. Metabolites identified in the urine of rats were saccharin (about 30% of urinary 14C), 2-sulphamoylbenzoic acid (about 35% urinary 14C) and 2-sulphamoylbenzyl alcohol (15% urinary 14C) in addition to unchanged compound (5--10% urinary 14C). The urine also contained a polar, labile metabolite that gave BIT on acid hydrolysis. The pattern of metabolism was not significantly affected by dose or route of administration. 3. In man, urine was the major route of elimination of 14C (93% dose) after administration of 14C-BIT (0.5 mg/kg). Negligible 14C was recovered in the faeces (less than 1% dose). Excretion was rapid (59% dose in 6 h; 80% dose in 12 h) and little 14C was eliminated on the second (3%) or subsequent days after dosing. 4. Identified metabolites in man included saccharin (about 50% of urinary 14C), 2-sulphamoylbenzoic acid (7% urinary 14C) and 2-sulphamoylbenzyl alcohol (8% urinary 14C unconjugated and 40% conjugated) with negligible unchanged compound. Only traces of the polar labile metabolite were detected. 5. the possible significance of metabolic interrelationships of toluene-2-sulphonamide and BIT to studies on the metabolism of saccharin are discussed.