Doses Of Saccharin Research Articles

Kidney and Ileum Histopathology of Rattus norvegicus Toxicity Model of Rhodamine B and Saccharin Supplemented with Purple Roselle Yoghurt

Background: Rhodamin B and saccharin are chemicals that are harmful to the health of the body. Consumption of rhodamine B and saccharin for a long time can cause problems for the body such as impaired organ function. Purpose: The aim was to find out the benefits of giving purple rosella yogurt in preventing damage to the kidneys and ileum of Rattus norvegicus caused by rhodamine B and saccharin. Methods: Using RAL with 28 male Rattus novergicus aged 8-12 weeks. Group K(-) was not given any treatment, K(+R) was given rhodamine B, K(+S) was given saccharin, K(+K) was given rhodamine B and saccharin, P1 was given rhodamine B and yoghurt, P2 was given saccharin and yoghurt, P3 was given rhodamine B, saccharin, and yogurt. The dose of rhodamine B was 22.5 mg/kg, the dose of saccharin was 157.7 mg/kg, the volume of yoghurt was 1 ml/head. Administered orally with gastric tube for 14 days. The concentration of purple rosella extract used was 15% (v/v). Results: Group K(+K) showed the heaviest damage. Groups P1, P2, and P3 still found damage to the kidneys, in P1 they experienced thickening of Bowman's capsule in the glomerulus, in P2 they experienced a loss of more than 25% of the brush border in the tubules, and in P3 they experienced glomerular tufts in the glomerulus. In the ileum, P1 experienced thickening of the muscles, P2 experienced clusters of inflammatory cells in the submucosa, and P3 experienced 10-50% loss of goblet cells. Conclusion: Provision of purple rosella yogurt can prevent damage to the kidneys and ileum of Rattus novergicus due to rhodamine B and saccharin, although it is not optimal.

Long-Term Saccharin Consumption and Increased Risk of Obesity, Diabetes, Hepatic Dysfunction, and Renal Impairment in Rats.

Background and objectives: This study evaluated the effect of chronic consumption of saccharin on important physiological and biochemical parameters in rats. Materials and Methods: Male Wistar rats were used in this study and were divided into four groups: A control group and three experimental groups (groups 1, 2, and 3) were treated with different doses of saccharin at 2.5, 5, and 10 mg/kg, respectively. Each experimental group received sodium saccharin once per day for 120 days while the control group was treated with distilled water only. In addition to the evaluation of body weight, blood samples [total protein, albumin, glucose, lipid profile, alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), creatinine, and uric acid] and urine (isoprostane) were collected in zero time, and after 60 and 120 days for biochemical evaluation. Liver (catalase activity) and brain (8-hydroxy-2’-deoxyguanosine, 8-OHdG) tissues were collected at time zero and after 120 days. Results: The data showed that saccharin at 5 mg/kg increased body weight of treated rats after 60 (59%) and 120 (67%) days of treatment. Increased concentration of serum glucose was observed after treatment with saccharin at 5 (75% and 62%) and 10 mg/kg (43% and 40%) following 60 and 120 days, respectively. The concentration of albumin decreased after treatment with saccharin at 2.5 (34% and 36%), 5 (39% and 34%), and 10 mg/kg (15% and 21%) after 60 and 120 days of treatment, respectively. The activity of LDH and uric acid increased proportionally with dosage levels and consumption period. There was an increased concentration of creatinine after treatment with saccharin at 2.5 (125% and 68%), 5 (114% and 45%), and 10 mg/kg (26% and 31%) following 60 and 120 days, respectively. Catalase activity and 8-OHdG increased by 51% and 49%, respectively, following 120 days of treatment with saccharin at 2.5 mg/kg. Elevation in the concentration of isoprostane was observed after treatment with saccharin at all doses. Conclusions: The administration of saccharin throughout the treatment period was correlated with impaired kidney and liver function. Both hyperglycemic and obesity-inducing side effects were observed. There was an increased oxidative status of the liver, as well as exposure to increased oxidative stress demonstrated through the increased levels of isoprostane, uric acid, 8-OHdG, and activity of catalase. Therefore, it is suggested that saccharin is unsafe to be included in the diet.

High-runner mice have reduced incentive salience for a sweet-taste reward when housed with wheel access

To explore reward substitution in the context of voluntary exercise, female mice from four replicate high-runner (HR) lines (bred for wheel running) and four non-selected control (C) lines were given simultaneous access to wheels and palatable solutions as competing rewards (two doses of saccharin [0.1, 0.2% w/v]; two doses of common artificial sweetener blends containing saccharin [Sweet ‘N Low®: 0.1, 0.2% w/v], aspartame [Equal®: 0.04, 0.08% w/v], or sucralose [Splenda®: 0.08, 0.16% w/v]; or two doses of sucrose [3.5, 10.5% w/v]). Wheel running and fluid consumption were measured daily, with each dose (including plain water) lasting two days and two “washout” days between solutions. In a separate set of mice, the experiment was repeated without wheel access. The artificial sweeteners had no statistical effect on wheel running. However, based on proportional responses, both doses of sucrose significantly elevated wheel running in C but not HR mice. In contrast, the high dose of sucrose suppressed home-cage activity for both linetypes. Both sucrose and the artificial blends generally increased fluid consumption in a dose-dependent manner. When they had access to wheels, HR had a significantly smaller increase in consumption of artificial sweetener blends when compared with C mice, but not when housed without wheels. Overall, these results provide further evidence that the reward system of HR mice has evolved, and specifically suggest that HR mice have a reduced incentive salience for some artificial sweetener blends, likely attributable to the stronger competing reward of wheel running that has evolved in these lines.

Mice Do Not Develop Conditioned Taste Aversion because of Immunity Loss

Objectives: This study intends to test the generation of conditioned taste aversion and conditioned immunodepression by daily paired administration of saccharin solution with cyclophosphamide, 15 mg/kg, for 4 days. Methods: One group of male mice of the outbred CD1 strain drank 0.15% saccharin and received 1 injection of cyclophosphamide, 15 mg/kg, for 4 days (paired group), another group (unpaired group) received the same doses of saccharin and cyclophosphamide noncontingently, the third group (cy60) received saccharin paired with cyclophosphamide, 60 mg/kg, and the fourth group (placebo) received saccharin in the absence of cyclophosphamide. All mice were immunized with keyhole limpet hemocyanin (KLH), 0.2 mg, 1 day before the treatments. Results: Mice of the paired, unpaired and cy60 groups displayed a similarly decreased antibody response to KLH, but mice of the paired group did not develop an aversion to saccharin while mice of the cy60 group did. Besides, repeat presentation of saccharin to mice of the paired group did not alter their antibody response to ovalbumin compared with mice of the unpaired or placebo group. Conclusions: Taste aversion was not elicited in response to impaired immunity and the conditioned stimulus (saccharin) did not impair the antibody response.

Effects of Cyclic Amp on P42/44 Mitogen-Activated Protein Kinase (MAPK) Activity in Rat Lacrimal Gland

When male rats of certain strains are fed a diet with 3% or more Na saccharin, their urinary bladders develop epithelial hyperplasia and a greater incidence of tumors. Since the daily dose of saccharin is high, a link between tumor formation and the disruption of urothelial physiologic and biochemical processes has been sought. We fed male and female Sprague-Dawley rats a saccharin-free or 7.5% Na saccharin diet for 1 month. Excised bladders were mounted in flux chambers and exposed to Krebs-Ringer bicarbonate solution (KRB) or urine. Bioelectric properties and 22Na, 36Cl, and [14C]mannitol or [3H]mannitol unidirectional fluxes were measured by conventional techniques. No differences were noted between bladders from male and female animals or between Na saccharin-fed animals and animals fed the saccharin-free diet. When both surfaces of the epithelium were exposed to KRB, transepithelial dc conductance fell over 4 hr to 50% of the initial value. Conductance averaged 1.4 mS/cm2. Transepithelial potential difference (PD) was usually lumen negative and averaged 0.7 mV. Unidirectional permeability coefficients for 36Cl, 22Na, and radiomannitol were symmetric, proportional to conductance, and followed a rank order compatible with unrestricted passive diffusion. Exposure of the bladder lumen to urine from animals fed saccharin-free or Na saccharin diet hyperpolarized the transepithelial PD by more than 5 mV and raised conductance nearly threefold. Permeability coefficients remained symmetric and compatible with passive diffusion. Exposure of the lumen to solutions with the K+, Na+, and Cl− concentrations and osmolality of urine simulated the conductance and PD effects of urine. We conclude that Na saccharin feeding or urine with saccharin does not uniquely affect the permeability of the excised preparation. Small hydrophilic solutes appear to cross the bladder epithelium through paracellular channels which increase in aggregate area during exposure of the lumen to urine. The hyperpolarization induced by lumenal urine is the consequence of the transepithelial K+ gradient.

Human carcinogenic risk evaluation, part IV: assessment of human risk of cancer from chemical exposure using a global weight-of-evidence approach.

In the early 1960s, the National Cancer Institute developed procedures to formalize the process for the evaluation of the human risk of cancer from chemical exposure (Boorman, 1994; Weisburger, 1983). This approach was based on decades of research that demonstrated that chemicals that were known to cause cancer in humans could be shown to induce cancer in laboratory animals as well. Despite the fact that this approach by the NCI was envisioned as an initial assessment of carcinogenic activity to identify those chemicals for which further study was needed, the use of two rodent species exposed for 2 years as the primary mechanism to identify potential human hazards was in widespread use by the early 1970s (Boorman, 1994). In 1975, this process was developed into a recommendation that has formed the basis of regulatory guidance (Sontag, 1976). This guidance represented the best thinking of the time about how to accomplish the critical but difficult task of prospectively identifying chemicals that might pose a carcinogenic risk to humans. Despite significant progress in our understanding of the biology of the carcinogenic response in animals and humans in the nearly 30 years since this guideline was published, these recommendations continue to form the foundation of how we do cancer risk assessment today. We have a large and extensive database today from which to develop a more rational, science-based approach to this process. A careful consideration of the available data suggests an alternative approach to this important task. Much of the early work done in this field that led to the use of the 2-year bioassay was done with reactive chemicals, most of which interacted with DNA (Miller, 1978). Ample evidence accumulated that compounds in classes like the polycyclic aromatic hydrocarbons that were known or suspected human carcinogens produced tumors in rodents. It was logical to assume that rodent tumor data could predict the hazard associated with human exposure. The concept of genetic versus epigenetic or alternative mechanisms of carcinogenesis originally proposed in the late 1980s is now well accepted. While much is understood about the mechanism of tumor induction by DNA-reactive carcinogens, assessment of human risk from exposure to nongenotoxic agents is more problematic. Careful and comprehensive evaluation of the modes of action of chemicals that produce tumors in rodents has led to the understanding that positive findings in long-term rodent studies do not necessarily predict human hazard. We now understand, for example, why urinary bladder tumors in rats exposed to high doses of saccharin or melamine do not imply a hazard for humans (Cohen et al., 1991; Rodent Bladder Carcinogenesis Working Group, 1995). Similarly, a broad and very comprehensive array of data on male rat kidney tumors induced by compounds like d-limonene that produce a characteristic male rat hydrocarbon nephropathy do not predict a carcinogenic hazard for humans following exposure to these chemicals (Swenberg and Lehman-McKeeman, 1999). In the pharmaceutical arena, there are numerous similar examples. Rat mammary tumors produced in response to b-adrenergic blocking agents in the 1970s caused significant disruption to drug development programs as concern was raised over the possibility of a similar tumorigenic response in humans. It is now clear that the biology surrounding the tumor promoting activity in rodents (hyperprolactinemia) is dissimilar between the two species and does not predict human hazard (Schyve et al., 1978; Welsch and Nagasawa, 1977). A similar major concern was raised over the appearance of the unusual mesovarial leiomyoma in rats exposed to b-agonists like salbutamol in this same time frame. It is now well accepted that this rodent tumorigenic response is secondary to a unique pharmacodynamic effect in this tissue in the rat and is not an indicator of human risk (Jack et al., 1983). To whom correspondence should be addressed: Schering-Plough Research Institute, 2015 Galloping Hill Rd., Kenilworth, NJ 07033. Fax: (973) 940-4159. E-mail: james.madonald@spcorp.com.

Saccharin effects on morphine-induced antinociception in the mouse formalin test

This study was performed to investigate the role of sweetness and taste sensations of the non-caloric sweetener saccharin on pain and morphine antinociception by the formalin test in mice. The formalin test was chosen because it measures the response to a long-lasting nociceptive stimulus and thus may closely resemble clinical pain. The total time (seconds) spent licking and biting the injected paw (indices of nociception) during periods of 0–5 min (early phase) and 10–30 min (late phase) were measured as an indicator of pain and inflammatory responses. A 12 days pretreatment of animals with saccharin (0.04%, 0.08%, 0.16%) produced complex effects on the action of morphine. All doses significantly potentiated the low dose (1.5mgkg−1 ) of morphine-induced analgesia in the early phase significantly but antagonized the effect of morphine (3 mgkg−1). The effect of high doses of morphine (6–9mgkg−1 ) was antagonized by the low dose of saccharin (0.04%), but the effect of morphine (6 mgkg−1) was potentiated with high concentrations of saccharin (0.08% and 0.16%). All doses of saccharin decreased the analgesic effect of morphine at a dose of 9mgkg−1 . Analgesic effects of low doses of morphine (1.5–3mgkg−1 ) were decreased by all doses of saccharin in the late phase. Different concentrations of saccharin also affected the antagonistic effect of naloxone (0.4 mgkg−1) on morphine-induced analgesia in both phases of the formalin test. The high dose of saccharin (0.16%) potentiated the effect of naloxone in the late phase. The results obtained suggest that sweet sensation is an important factor in mediating morphine analgesic properties. It is therefore inappropriate to use different concentrations of sweet saccharin solutions interchangeably.

Glandular stomach hemorrhage induced by high dose saccharin in young rodents

In studies primarily designed to evaluate the effects of saccharin and silicate on the urinary bladders of rodents, hemorrhage of the glandular stomach was observed in high incidence. It occurred in young rats with high doses of saccharin (7.5% sodium saccharin; 6.3% acid saccharin), with no difference between male and female F344 rats fed during ages 5 to 15 weeks, no difference between sodium saccharin and acid saccharin, and was reversible, even with continued saccharin administration. Sodium silicate (0.38, 1.13, 2.26% of the diet) had no influence on gastric hemorrhage. Iron deficiency anemia has been observed in young rats fed high dietary levels of saccharin, and the present results suggest that gastric hemorrhage contributes to its etiology.

Effects of Na saccharin feeding and urine on barrier properties of excised rat urinary bladder

When male rats of certain strains are fed a diet with 3% or more Na saccharin, their urinary bladders develop epithelial hyperplasia and a greater incidence of tumors. Since the daily dose of saccharin is high, a link between tumor formation and the disruption of urothelial physiologic and biochemical processes has been sought. We fed male and female Sprague-Dawley rats a saccharin-free or 7.5% Na saccharin diet for 1 month. Excised bladders were mounted in flux chambers and exposed to Krebs-Ringer bicarbonate solution (KRB) or urine. Bioelectric properties and 22Na, 36Cl, and [ 14C]mannitol or [ 3H]mannitol unidirectional fluxes were measured by conventional techniques. No differences were noted between bladders from male and female animals or between Na saccharin-fed animals and animals fed the saccharin-free diet. When both surfaces of the epithelium were exposed to KRB, transepithelial dc conductance fell over 4 hr to 50% of the initial value. Conductance averaged 1.4 mS/cm 2. Transepithelial potential difference (PD) was usually lumen negative and averaged 0.7 mV. Unidirectional permeability coefficients for 36Cl, 22Na, and radiomannitol were symmetric, proportional to conductance, and followed a rank order compatible with unrestricted passive diffusion. Exposure of the bladder lumen to urine from animals fed saccharin-free or Na saccharin diet hyperpolarized the transepithelial PD by more than 5 mV and raised conductance nearly threefold. Permeability coefficients remained symmetric and compatible with passive diffusion. Exposure of the lumen to solutions with the K +, Na +, and Cl − concentrations and osmolality of urine simulated the conductance and PD effects of urine. We conclude that Na saccharin feeding or urine with saccharin does not uniquely affect the permeability of the excised preparation. Small hydrophilic solutes appear to cross the bladder epithelium through paracellular channels which increase in aggregate area during exposure of the lumen to urine. The hyperpolarization induced by lumenal urine is the consequence of the transepithelial K + gradient.

Dietary saccharin kinetics.

Six adult female subjects who use saccharin-containing products in their diet were asked to take divided equal doses of saccharin every 6 hr to maintain their average daily intake for 3 days. At the end of this period, each subject took a single dose that was equal to one divided dose. Saccharin concentrations in plasma and urine samples were used to assess the kinetic profile. Saccharin absorption was rapid with maximum concentrations in plasma in 0.5 to 1.0 hr. Maximum plasma concentrations and areas under the plasma concentration-time curves were proportional to dose. Renal clearance exceeded glomerular filtration rate in all cases and approximated renal plasma flow when corrected for the saccharin free fraction in plasma. Mean elimination half-life was 7.5 hr and mean apparent volume of distribution was 264 l. The kinetic parameters indicate that saccharin is distributed as a function of lean rather than total body mass (suggesting that saccharin does not distribute into body fat). This observation, together with data from studies in animals, suggests that there may be one or more high-retention compartments for saccharin.

A preliminary report on the pharmacokinetics of saccharin in man: single oral dose administration.

The pharmacokinetics of saccharin were studied in two human subjects. One male and one female subject ingested a single 100 mg oral dose of saccharin. Absorption was fast and the elimination half-lives were 1.2 and 6.6 hours for the male and female subject, respectively. Approximately 85% of the oral dose was recovered in the urine as intact saccharin and renal clearance approximated renal plasma flow when corrected for the unbound fraction of saccharin in plasma. Saccharin elimination appears to be related to previous saccharin ingestion, suggesting a high-retention compartment.

Saccharin and cyclamate inhibit binding of epidermal growth factor.

The binding of 125I-labeled mouse epidermal growth factor (EGF) to 18 cell lines, including HeLa (human carcinoma), MDCK (dog kidney cells), HTC (rat hepatoma), K22 (rat liver), HF (human foreskin), GM17 (human skin fibroblasts), XP (human xeroderma pigmentosum fibroblasts), and 3T3-L1 (mouse fibroblasts), was inhibited by saccharin and cyclamate. The human cells were more sensitive to inhibition by these sweeteners than mouse or rat cells. EGF at doses far above the physiological levels reversed the inhibition in rodent cells but not in HeLa cells. In HeLa cells, the doses of saccharin and cyclamate needed for 50% inhibition were 3.5 and 9.3 mg/ml, respectively. Glucose, 2-deoxyglucose, sucrose, and xylitol did not inhibit EGF binding. Previous studies have shown that phorbol esters, strongly potent tumor promoters, also inhibit EGF binding to tissue culture cells. To explain the EGF binding inhibition by such greatly dissimilar molecules as phorbol esters, saccharin, and cyclamate, it is suggested that they operate through the activation of a hormone response control unit.

Dose Response of Saccharin in Induction of Urinary Bladder Hyperplasias in Fischer 344 Rats Pretreated With <italic>N</italic>-Butyl-<italic>N</italic>-(4-hydroxybutyl)nitrosamine<xref ref-type="fn" rid="FN2">2</xref>

Studies were made on the dose response of saccharin in the induction of bladder lesions. Inbred F344 rats of both sexes were pretreated with 100 ppm N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) in the drinking water for 4 weeks. Sodium saccharin was given at 50,000, 10,000, 2,000, and 400 ppm in the diet for 32 weeks after BBN administration, and surviving rats were killed at the end of week 36 of the experiment. No increase in incidence of papilloma or cancer was noted in either sex at any dose of saccharin after BBN as compared to levels induced by BBN alone. The incidences of two types of hyperplasia and average number of papillary or nodular hyperplasias per 10 cm of basement membrane were significantly increased in the group receiving 50,000 ppm saccharin as compared to the group given BBN only. None of the incidences or numbers of these lesions were significantly different in any of the other saccharin-treated groups when compared to the group treated with BBN alone except for the incidences of two types of hyperplasias in the female rats dosed with 10,000 ppm saccharin. Dose-response curves showed enhanced hyperplastic responses in both sexes given 2,000--50,000 ppm saccharin. Administration of various doses of saccharin without BBN did not cause any changes in the urinary bladders of rats of either sex. These results show that saccharin enhances the induction of early-stage bladder lesions and that the biologic response demonstrates a dose-response effect.

Syncarcinogenic action of saccharin or sodium cyclamate in the induction of bladder tumours in MNU-pretreated rats.

Abstract The potential of saccharin, sodium cyclamate or calcium carbonate to promote bladder cancer was investigated. Single doses of 2 mg N-methyl-N-nitrosourea (MNU) were instilled into the bladders of female rats. One group was maintained thereafter on a control diet. On the same day the three other groups of MNU-treated rats were started on a diet supplemented with 2% saccharin, 2% sodium cyclamate or 3% calcium carbonate and maintained on this diet for the rest of their lives (the doses of saccharin and sodium cyclamate were increased to 4% after 10 wk). There was no significant difference between any of the groups in average survival time, body-weight gain or food intake. All the MNU-treated groups developed urinary-tract neoplasms but there were no significant differences in tumour incidence between the MNU-treated group and the combined-treatment groups. However there were slight increases in the incidences of tumours in all the combined treatment groups, compared with that in the group given MNU alone. No significant difference in the latency periods of the tumours was found between any of the MNU-treated groups.

Response of the rat to saccharin with particular reference to the urinary bladder.

Male and female Wistar rats were administered sodium saccharin for life (2 yr) either in the drinking water or diet. The maximum palatable dose of saccharin in the drinking water was found to be 2 g/kg/day and, even then, there was some voluntary restriction of fluid intake in the males. By contrast, double this dose--namely 4 g/kg/day, was palatable in the diet. A control group of rats of both sexes received saccharin-free diet and drinking water. Mild urothelial hyperplasias developed from 85 weeks in rats of both sexes receiving saccharin either in the drinking water or diet; the incidence was statistically significant in both the bladders and kidneys of rats receiving the higher dose of saccharin in the diet, but in the kidneys only of rats receiving the lower dose of saccharin in the drinking water. Telangiectasia of the vasa recta was significant in saccharin-treated rats of both sexes at both doses. A very low incidence of bladder tumours, exclusively in males receiving the higher saccharin dose in the diet was seen from 95 weeks. No consistent relationship between bladder epithelial hyperplasias and crystalluria could be demonstrated, although all 3 bladder tumours were associated with some form of mineralisation. Results suggest a particular susceptibility of males to saccharin treatment. The possibility that saccharin may promote, or enhance, the development of latent tumour cells already present in the experimental population, rather than initiate carcinogenesis per se is considered.

Carcinogenicity of saccharin.

Saccharin is carcinogenic for the urinary bladder in rats and mice, and most likely is carcinogenic in human beings. The neoplasms of the urinary bladder are malignant and invade and metastasize. Male rats are more susceptible to urinary bladder carcinogenesis than female rats. Rats exposed as fetuses develop neoplasms more readily than rats exposed as weanlings. The lesions in the urinary bladder go through the stages of hyperplasia, hyperplastic nodules, and later carcinomas. The male of the human species ingesting saccharin, as for rats, is more susceptible to carcinogenesis of the urinary bladder than the female. Neoplasms of the urinary bladder in rats were not caused by stones, parasites, sodium, or impurities. There is a cocarcinogenic effect between saccharin and methylnitrosurea for the urinary bladder. Even through carcinomas of the urinary bladder are present in rats given the higher doses of saccharin, one was observed in a female rat given 0.5%. Chronic renal disease develops in rats ingesting saccharin. The disease is more advanced at the lower doses than at the higher doses, suggesting that saccharin at the lower doses does not reach the urinary bladder. Early neoplasms are seen in the renal pelvis of rats given the higher doses of saccharin. The risk ratios for urinary bladder carcinomas in human beings increase with both frequency andduration of saccharin usage. Benign and malignant neoplasms at all sites are significantly increased in mice and rats ingesting the higher doses of saccharin. These neoplasms are present in the reproductive and hematopoietic systems, and to a lesser extent in the lungs, vascular system and squamous epithelium. Neoplasms in some organs develop with the lower doses of saccharin. Lymphosarcomas of the lung are significantly increased in rats given 0.01% saccharin. Chronic renal disease in rats given saccharin interferes with the health and life span and consequently with development of neoplasms. Saccharin initiates neoplasms of the skin when its application is followed by croton oil. Epidemiological studies have not been done for neoplasms other than the urinary bladder in human beings.

Evaluation of a new model to detect bladder carcinogens or co-carcinogens; results obtained with saccharin, cyclamate and cyclophosphamide

A sensitive rat model has been designed to detect potential weak bladder carcinogens or co-carcinogens. The test compound is given to animals which have received a single initiating, but non-carcinogenic, dose of N-methyl- N-nitrosourea (MNU). The model has been used to investigate two compounds currently under suspicion as weak bladder carcinogens, namely sodium saccharin and sodium cyclamate and one compound known to be cytotoxic but not carcinogenic for the bladder epithelium namely cyclophosphamide. For comparison, these three compounds were also tested as solitary carcinogens in animals not pre-treated with MNU. At the very high dose levels used, sodium saccharin and sodium cyclamate were weak solitary carcinogens producing 4/253 and 3/228 bladder tumours respectively, and the first of these tumours did not appear for more than 80 weeks. When ested in the MNU/rat model more than half the animals receiving either sodium saccharin or sodium cyclamate developed bladder tumours from 10 weeks onwards. By contrast, cyclophosphamide failed to produce any tumours when tested either as a solitary carcinogen or in the MNU/rat model. It must be emphasized that the doses of saccharin and cyclamate used were far higher than those consumed by man, including diabetics and these results should not be directly extrapolated to man without careful consideration of many other factors including negative epidemiological findings. The theoretical basis of the model is discussed and also the relevance, in terms of environmental human exposure, of detecting compounds which have a synergistic effect with other known bladder carcinogens. It appears that this model car be used to detect a carcinogenic or co-carcinogenic potential in compounds which are organotropic for the bladder more rapidly and with fewer animals than if the compounds are tested as solitary carcinogens by more conventional methods. It is suggested that it could be used to detect those compounds which require further investigation.

Saccharin: Lack of chromosome-damaging activity in chinese hamsters in vivo

Oral administration of a high dose of saccharin (1·5g/kg/day for 3 days) to Chinese hamsters followed by chromosome analysis of bone-marrow cultures did not reveal any statistically significant increase in chromosomal abnormalities. The numbers of polyploid and aneuploid cells and the structural chromosomal aberrations in the bone marrow showed no changes in comparison with a control group. An increase in the population of dividing cells was induced in the test animals by an injection of pertussis vaccine prior to the administration of saccharin.

The metabolism of saccharin in laboratory animals

When rats and monkeys of both sexes received a single oral dose of 40 mg sodium [ 14C]saccharin/kg, more than 90% was recovered in the urine collected for 96 hr after dosing. Thin-layer chromatography of the whole urine indicated that the only significant radioactivity on the developed chromatograph had the same R F as saccharin; this radioactive fraction recrystallized with pure unlabelled saccharin. Hydrolysis products of saccharin were not detected. Artefactual ‘metabolites’ of saccharin were observed if radioactive contaminants were not accounted for, if control urine was not compared with test urine and if saccharin was extracted from urine under acidic conditions. During the first 4–8·75-hr collection period, no more than 0·3% of an oral dose of saccharin was excreted in rat bile, while up to 11·7% passed into the bladder. The 14C-fraction in the bile had the same R F as saccharin. Induction of mixed function oxidase activity in rat liver by treatment with phenobarbitone had no influence on saccharin metabolism. Daily oral doses of 20, 100 or 500 mg sodium saccharin/kg, given to monkeys for over 2 yr, had no effect on the metabolism of a single oral dose of [ 14C]saccharin. We conclude that, in the species studied and within the limits of our analytical methods, saccharin is not metabolized.