Mutagenicity study of Remsen-Fahlberg saccharin and contaminants

Mutagenic Activity of p-Toluenesulfonhydrazide

Toluenesulfonhydrazide (TSH) is a high volume production chemical for which there is relatively little toxicological data. In this study, the mutagenic activity of TSH was determined in the Salmonella/mammalian microsome assay and the in vitro chromosomal aberration assay using Chinese hamster ovary cells. TSH induced gene mutations both with and without metabolic activation in the Salmonella/mammalian microsome assay but that it did not induce chromosomal aberrations in Chinese hamster ovary cells. The results of this study indicate that TSH is an in vitro mutagen and should be assessed for in vivo mutagenicity.

Saccharin mechanistic data and risk assessment: urine composition, enhanced cell proliferation, and tumor promotion

Sodium saccharin (NaSac) produces bladder tumors consistently in male rats only after lifetime exposure that begins at birth. NaSac is not metabolized and is negative in most genotoxicity tests. NaSac-induced cell damage and proliferation have been proposed as important factors in tumor promotion, and dose-response information demonstrating a threshold for these parameters is available. One theory proposes that high levels of NaSac, combined with protein in a high Na+, high pH environment found only in the male rat, form toxic microscopic crystals; therefore, NaSac-induced tumors may not be relevant to human carcinogenesis.

The genetic toxicology of putative nongenotoxic carcinogens

This report examines a group of putative nongenotoxic carcinogens that have been cited in the published literature. Using short-term test data from the U.S. Environmental Protection Agency/International Agency for Research on Cancer genetic activity profile (EPA/IARC GAP) database we have classified these agents on the basis of their mutagenicity emphasizing three genetic endpoints: gene mutation, chromosomal aberration and aneuploidy. On the basis of results of short-term tests for these effects, we have defined criteria for evidence of mutagenicity (and nonmutagenicity) and have applied these criteria in classifying the group of putative nongenotoxic carcinogens. The results from this evaluation based on the EPA/IARC GAP database are presented along with a summary of the short-term test data for each chemical and the relevant carcinogenicity results from the NTP, Gene-Tox and IARC databases. The data clearly demonstrate that many of the putative nongenotoxic carcinogens that have been adequately tested in short-term bioassays induce gene or chromosomal mutations or aneuploidy.

The in vivo micronucleus assay in mammalian bone marrow and peripheral blood. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The protocol recommended for the micronucleus assay in mammalian bone marrow has been revised and simplified. The number of sample times has been reduced to one or two, depending upon the dosing protocol. The minimum number of cells to be scored per treatment group has been increased to 20,000 to increase the ability of the assay to detect a doubling of the control micronucleus frequency. Use of both male and female animals is recommended. Scoring of micronuclei in polychromatic erythrocytes of peripheral blood is included as a variation of the bone marrow assay. Published data on chemicals tested by the micronucleus assay have been reviewed and are summarized.

The present lack of evidence for unique rodent germ-cell mutagens

Six chemicals, diethylhexyl phthalate (DEHP), ethanol, cyclohexylamine (CHA), sodium saccharin (NaS), cadmium chloride (CdCl2) and triflupromazine (TFP), were suggested to be unique germ-cell mutagens (Auletta and Ashby, 1988) by the GeneTox Workgroups of the U.S. Environmental Protection Agency (EPA). If this is a correct classification it would have major consequences when screening for mutagenicity and when labelling genotoxic substances. However, our re-evaluation of the GeneTox literature, including some more recent publications, has failed to find substantive evidence that any of these chemicals have been unequivocally established as having unique mutagenic activity in germ cells. For DEHP, NaS and TFP the evidence for genotoxic/mutagenic effects is questionable, in both germinal and somatic cells. Ethanol and CdCl2 showed clastogenic activity, but it was not restricted to germ cells. Both, ethanol and cadmium salts, appear to induce aneuploidy. The unconfirmed clastogenic effect of CHA was restricted to rats, but it occurred in both bone marrow and spermatogonia. Therefore, the general observation that rodent germ-cell mutagens are also genotoxic in somatic cells in vivo (Brusick, 1980; Holden, 1982) remains valid.

The genotoxicity of sodium saccharin and sodium chloride in relation to their cancer-promoting properties

The literature indicates that sodium saccharin is non-reactive to DNA and inactive as a gene mutagen in vitro. At elevated dose levels it is capable of producing structural disturbances in eukaryotic chromosomes in vitro, and it shows intermittent activity as a very weak germ-cell and somatic-cell mutagen in vivo. Its possible mode of action in these respects is speculated on and related to its ability to promote bladder tumours in rats at elevated dose levels. A review of the toxicology of sodium chloride reveals a profile of genotoxic activities almost identical to that of sodium saccharin. It is suggested that the recorded genotoxic and cancer-promoting activities of these chemicals will only become apparent at elevated dose levels that define them as significant contributors to the biological medium (solvent) rather than as trace xenobiotic toxins (solutes). The possible activity of acid saccharin, or of its potassium, calcium and ammonium salts, as ionic genotoxins requires urgent evaluation.

Characterization of aminosaccharins in commercial sodium saccharin produced by the Maumee process

The most abundant polar impurities detected by ion-pair high-pressure liquid chromatography of sodium saccharin produced by the Maumee process were identified as 5- and 6-aminosaccharin. The combined levels of these compounds in the samples analysed ranged from 99 to 152 mg/kg. Other less abundant polar impurities identified in Maumee process sodium saccharin were 7-aminosaccharin and o-sulphamoylbenzoic acid. Mutagenicity assays of 5-aminosaccharin, 6-aminosaccharin and a polar impurity fraction isolated from Maumee saccharin, gave negative results.

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)

Effect of saccharin on the induction of chromosomal translocations in male mice and their F1 offspring

The dose-dependent effects of sodium saccharin on the fertility and the induction of chromosomal translocations in treated mice and their F1 males were examined. C3H X 101 mice were treated with saccharin for 2 successive weeks at doses of 200 and 500 mg/kg of body wt. Data from the fertility study showed that saccharin did not induce any significant effect on fertility. Cytological analysis of meiotic cells showed no chromosomal rearrangements. Semisterility and sterility were noted in F1 males of saccharin-treated animals. In semi-sterile and sterile F1 males of saccharin-treated animals chromosomal translocations were not found.

Study of artificial flavouring substances for mutagenicity in the Salmonella/microsome, Basc and micronucleus tests

Seventy-six compounds used as artificial flavouring substances in food products were studied for mutagenic properties by the use of the Salmonella/mammalian microsome test (Ames test), Basc test on Drosophila melanogaster and micronucleus test on mouse bone marrow. The following four compounds were mutagenic in Ames tests: ethyl nitrite, ethyl 3-phenylglycidate, 6-methylquinoline and musk ambrette. Of these, ethyl nitrite and musk ambrette also induced a significant (P less than or equal to 0.01) increase in sex-linked recessive lethal mutations in Drosophila. Two further compounds, ethyl 3-methyl-3-phenylglycidate and 4-n-propylanisole, appeared weakly mutagenic in Drosophila only. The result with 4-n-propylanisole was judged to be of equivocal biological significance. None of the flavouring substances induced micronuclei, i.e. cytogenetic damage in the bone marrow of mice.

Saccharin: a toxicological and historical perspective

Saccharin, first synthesized in 1879, eventually became popular as an inexpensive substitute for sugar, particularly as a non-caloric sweetner. The dispute concerning the safety of saccharin for human consumption is almost as old as saccharin itself. In this article, the history concerning the uses of saccharin and the accompanying controversy are reviewed. In addition, the spectrum of toxicological and epidemiological studies to which saccharin has been subjected are also examined. While the toxicological data indicate that saccharin is probably the agent solely responsible for the bladder tumors observed in second generation male rats, the epidemiological studies provide, at best, an equivocal relationship between the consumption of saccharin and bladder cancer. A benefit-risk evaluation for saccharin showed few, if any documentable benefits from the use of saccharin and much genuine uncertainty concerning the potential risks for ingestion by man. This element of genuine uncertainty as to the extent of human risk posed to man is the crux of saccharin's past and its foreseeable future.

Mutagenicity study of fried sausages in Salmonella, Drosophila and mammalian cells in vitro and in vivo

The basic extract of pan-fried sausages was studied for mutagenic potential in seven test systems. Mutagenic activity was high in the standard Ames assay in the Salmonella typhimurium strains TA1538 and TA98 in presence of S9 mix. In vivo, in the intrasanguine host-mediated assay with strain TA98 on Aroclor-pretreated mice, the mutagenic activity of the extract was low. A borderline activity was seen in the SCE assay in vitro with V79 Chinese hamster cells in presence of S9 mix. No significant mutagenic action was found in the gene-mutation assay for thioguanine resistance with V79 cells, the Drosophila sex-linked recessive lethal test, the micronucleus test and the mammalian spot test.

Studies to evaluate artificial sweeteners, especially Remsen--Fahlberg saccharin, and their possible impurities, for potential mutagenicity by the Salmonella/mammalian liver microsome test

Cyclamate, cyclohexylamine, saccharin, boiled saccharin, 3 organic extracts of this sweetener and 9 possible impurities, including OTS and PTS, were evaluated for potential mutagenic activity by the Salmonella/mammalian liver microsome test on Salmonella typhimurium TA1535, TA100, TA1537 and TA98 (extracts only on TA98) with doses up to at least 2500 micrograms per plate with and without metabolic activation. No mutagenic activity was established either for cyclamate, cyclohexylamine or saccharin, or for some of the possible impurities of saccharin synthesized by the Remsen--Fahlberg or Maumee process. Only 1 organic extract gave inconclusive results in 3 consecutive experiments. No mutagenic activity was noted for saccharin refluxed for 2 h in solution.

Mutagenicity of cosmetics ingredients licensed by the European Communities

As part of our investigation into mutagenic effects of environmental compounds, we studied chemicals allowed as ingredients of cosmetics according to the guidelines of the Council of the European Communities (27 July 1976). We used three systems, the Salmonella/microsome test, the Basc test on Drosophila and the micronucleus test on mouse bone marrow. Of the 31 chemicals tested, 15 were mutagenic in the Ames test; and of these, 5 were also mutagenic in the Basc test and 2 in the micronucleus test.

The apparent inhibition of urothelial DNA synthesis in neonatal rats by dietary saccharin

[3H]Thymidine ([3H]TdR) incorporation into urothelial DNA of male neonatal rats was measured autoradiographically at birth and during the first 3 weeks of life. The rats were derived from control parents and those fed saccharin (1, 3, 5 and 7.5%) in the diet from before pregnancy. [3H]TdR incorporation was inhibited and there were more lightly labeled cells (compared with controls), in all the saccharin-exposed rats in a rough dose-dependent manner. The results, in comparison with controls, suggest that saccharin exposure in utero causes DNA damage in the neonatal urothelium manifesting as reduced thymidine incorporation and a greater proportion of lightly labeled cells.