Cytogenetic effects of cyclamates on human cells in vitro

Non-sugar sweeteners and cancer: Toxicological and epidemiological evidence

Several toxicological and epidemiological studies were published during the last five decades on non-sugar sweeteners (NSS) and cancer. Despite the large amount of research, the issue still continues to be of interest. In this review, we provided a comprehensive quantitative review of the toxicological and epidemiological evidence on the possible relation between NSS and cancer. The toxicological section includes the evaluation of genotoxicity and carcinogenicity data for acesulfame K, advantame, aspartame, cyclamates, saccharin, steviol glycosides and sucralose. The epidemiological section includes the results of a systematic search of cohort and case-control studies. The majority of the 22 cohort studies and 46 case-control studies showed no associations. Some risks for bladder, pancreas and hematopoietic cancers found in a few studies were not confirmed in other studies. Based on the review of both the experimental data on genotoxicity or carcinogenicity of the specific NSS evaluated, and the epidemiological studies it can be concluded that there is no evidence of cancer risk associated to NSS consumption.

Effects of sodium cyclamate and sodium saccharin on focus induction in explant cultures of rat bladder

The tumour-promoting activities of sodium cyclamate and sodium saccharin were investigated in an assay based on the induction of epithelial foci exhibiting enhanced growth potential in a rat bladder explant culture system. An initiating, non-focus-inducing dose was defined for the carcinogen N-methyl-N-nitrosourea (MNU) to make promotion studies possible. Saccharin induced epithelial foci when added to cultures pretreated with an initiating dose of MNU, and also increased the incidence of foci in cultures treated with transforming doses of MNU. Cyclamate was found to induce a high incidence of foci when added to cultures by itself. When MNU and cyclamate treatments were combined, an additive effect could be detected. These results indicate that both cyclamate and saccharin can contribute to epithelial transformation in this system.

Toxicological aspects of cyclamate and cyclohexylamine

In the late 1960s the artificial sweetener cyclamate was implicated as a bladder carcinogen in rats. This finding and other concerns about its safety ultimately led to a ban on cyclamate in the U.S. and restrictions on its use in many other countries. Since that time, the carcinogenic potential of cyclamate and cyclohexylamine, its principal metabolite, has been reevaluated in a group of well-controlled, well-designed bioassays that have failed to substantiate the earlier findings. This review of the published and unpublished literature on cyclamate attempts to evaluate the carcinogenicity question and other important aspects of the toxicity of cyclamate and cyclohexylamine, including their effects on various organ systems, their genotoxic potential, and their effects on reproduction. In addition, the physiological disposition of cyclamate is reviewed, with particular attention directed toward the site and extent of its conversion to cyclohexylamine.

Effects on mouse embryos of in utero exposure to saccharin: teratogenic and chromosome effects

For teratogenesis studies, pregnant ICR albino mice were administered saccharin by three routes and at three different doses by each route as follows: Intraperitoneal injection of 500, 1,000, or 2,000 mg/kg saccharin on day 10 of gestation; intragastric tube delivery of 5, 10, or 25 mg/kg/day of saccharin on days 5-15 of gestation; and as drinking water containing a 5, 10, or 20% solution of saccharin from day 0 through day 17. Appropriate controls were used for each set. No increase in either resorptions or malformations was found in mouse embryos whose dams had received saccharin by any of the three routes. For chromosome studies, saccharin was administered IP to pregnant ICR albino mice on day 10 of gestation as either a 1,000 mg/kg or 2,000 mg/kg dose. To demonstrate sister chromatid exchanges (SCE), bromodeoxyuridine was administered as 16 consecutive half-hourly doses of 25 mg/kg during the 8 h prior to saccharin injection. In addition, one group received two doses of BrdU and 2,000 mg/kg saccharin 8 h apart to demonstrate SCE frequency following exposure to saccharin for two cell cycles. The mice were given colchicine (4 mg/kg) 6 h after the final injection and killed 2 h later. Embryonic cell suspensions and metaphase spreads were prepared by routine methods. Metaphase spreads were examined for breaks or gaps (after Giemsa staining), for G-banding (using the ASG technique), for C-banding (using Giemsa staining after exposure to 0.07 N NaOH and incubation in 2 X SSC at 60 degrees C), and for SCE by the Hoechst-Giemsa method. Fifty metaphase spreads were counted for each experimental condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic effects of cyclamates

PHA-stimulated human peripheral lymphocytes were used as a model system for assessing the in vitro effects of calcium cyclamate. Techniques of autoradiography, cytological staining, cell counting, liquid scintillation and karyotyping were used to study the cytogenetic damage and biochemical effects of calcium cyclamate when assayed in 24 hour intervals for 96 hours. The cells were exposed to 10(-2) and 10(-3) molar concentrations of calcium cyclamate in TC 199 medium with fetal calf serum and antibiotics. These studies were carried out in three (3) phases. Phase I was primarily orientation studies of the effects of cyclamates and included running preliminary test checks, the establishment of parameters of dosage, assessing growth patterns and selecting key chromosomal aberrations. Sixty four (64) of the metaphase spreads showed morphologically detectable changes and aberrations. It was also noted that the addition of cyclamate increased mitotic rate of lymphocyte cells in cultures. Phase III arranged research designs to determine more precise characterization of chromosomal observations and morphological effects. Among other findings it was noted that of 13 types of observations only ten were found in the experimental group. The introduction of cyclamates increased the stability of the leucocyte cultures. These studies reinforced the findings on the increase of mitotic rate. Phase III extended protocols to include autoradiography and scintillation counting. It was determined that calcium cyclamate impaired the synthesis of deoxribonunucleic acid (as depicted by decreased incorporation of tritiated thymidine), reduced grain counts in autoradiographs and increased chromosome aberrations in cyclamate treated PHA stimulated peripheral blood lymphocytes in vitro. Morphological changes and growth rates showed significant effects. These studies indicate that calcium cyclamate has variable significant effects on leucocytes growth and chromosome morphology.

Three cases of human bladder cancer following high dose cyclamate ingestion

Vesical implantation and oral feeding studies in animals raised sufficient suspicion of the carcinogenic propensity of cyclamates to result in their withdrawal from sale throughout the world. The structural similarity to known carcinogens, an effect on human chromosomes in tissue culture and a high carcinogenic potential when combined with non-injurious co-carcinogens gave further support to this ban. On the other hand, numerous epidemiological studies failed to support any statistical relationship between cyclamate ingestion and vesical carcinoma in man. Three patients are described in whom vesical carcinoma developed after a prolonged period of ingestion of an unusually high amount of cyclamate sweetener. Moreover, the severity of the disease appeared to be proportional to the dose ingested. Although this is not a conclusive indictment of the role of cyclamates we believe that patients with bladder cancer should be questioned about intake of cyclamates either directly or in diet soft drinks.

Non-nutritive sweeteners and human bladder cancer: preliminary findings

The non-nutritive sweeteners, saccharin and cyclamate, were not associated with the risk of human bladder cancer in a controlled investigation. The prior intake of such sweeteners in any and all forms was not greater or more prolonged among 209 recently diagnosed bladder cancer patients than among 209 otherwise similar patients without bladder disease. These findings were unaffected by case-control differences in diabetic histories or smoking practices.

The mutagenicity of saccharin

Seventeen different reports are available dealing with the mutagenic effects of saccharin. Many of these are short abstracts, carrying incomplete information. Mainly tested as its sodium salt, saccharin has been found to be weakly mutagenic in Salmonella at very high doses, in Drosophila at moderate doses, and in mice at moderate to high doses. The compound is a weak chromosome breaker in onion root tips and in Chinese hamster cells. For most of these, and for other test systems as well, a number of doubtful or negative results have also been reported. Altogether the evidence for chromosome-breaking properties is stronger than for the induction of point mutations. The overall picture is too conflicting and equivocal to classify saccharin as a proven mutagen. It is suggested that the observed contradictions might be related to the occurrence of varying amounts of impurities.

Cytogenetic studies on calcium cyclamate in Meriones unguiculatus (gerbil) in vivo

Cytogenetic studies in Mongolian gerbils, Meriones unguiculatus, have shown that calcium cyclamate when given intraperitoneally can induce hyperploidy and chromosomal breaks, gaps, and fragments in bone marrow cells in vivo. Increasing concentrations of the sweetener produced increasing incidence of chromosomal abnormalities. Analysis of means showed that a 'saturation effect' of calcium cyclamate to induce hyperploidy, breaks and fragments was reached at 150 mg/kg; whereas a dose-response relationship was found between increasing concentrations (except at 50 mg/kg) and increasing percentage of cells showing gaps. The ability of calcium cyclamate to produce hyperploid cells and fragments is revealed for the first time in this study.

Synergistic effect of herpes simplex virus and cytosine arabinoside on human chromosomes

The combined treatment of cultures of human embryonic lung cells with herpes simplex virus type 2 and cytosine arabinoside produced a significantly increased number of cells containing multiple chromatid and chromosome breaks. The incidence of such cells was found to be approximately two and one half times greater than the additive effects of virus and cytosine arabinoside induced separately and is therefore synergistic.

Cytogenetic studies with cyclamate and related compounds

Cyclamate, cyclohexylamine, N-hydroxycyclohexylamine, and dicyclohexylamine can induce chromosomal damage in human leukocyte cultures.

Cytogenetic studies in rats of cyclohexylamine, a metabolite of cyclamate

Cyclohexylamine, the major known metabolite of cyclamate, was tested in vivo for possible cytogenetic effects. In rats injected with this metabolite, there was a direct relation between dose concentration and percentage of spermatogonial and bone marrow cells showing chromosomal breaks. Single chromatid breaks predominated with infrequent exchange figures.