Long-term toxicity studies on Chocolate Brown HT in rats

Effects of photon irradiation in the presence and absence of hindlimb unloading on the behavioral performance and metabolic pathways in the plasma of Fischer rats

Introduction: The space environment astronauts experience during space missions consists of multiple environmental challenges, including microgravity. In this study, we assessed the behavioral and cognitive performances of male Fisher rats 2 months after sham irradiation or total body irradiation with photons in the absence or presence of simulated microgravity. We analyzed the plasma collected 9 months after sham irradiation or total body irradiation for distinct alterations in metabolic pathways and to determine whether changes to metabolic measures were associated with specific behavioral and cognitive measures. Methods: A total of 344 male Fischer rats were irradiated with photons (6 MeV; 3, 8, or 10 Gy) in the absence or presence of simulated weightlessness achieved using hindlimb unloading (HU). To identify potential plasma biomarkers of photon radiation exposure or the HU condition for behavioral or cognitive performance, we performed regression analyses. Results: The behavioral effects of HU on activity levels in an open field, measures of anxiety in an elevated plus maze, and anhedonia in the M&M consumption test were more pronounced than those of photon irradiation. Phenylalanine, tyrosine, and tryptophan metabolism, and phenylalanine metabolism and biosynthesis showed very strong pathway changes, following photon irradiation and HU in animals irradiated with 3 Gy. Here, 29 out of 101 plasma metabolites were associated with 1 out of 13 behavioral measures. In the absence of HU, 22 metabolites were related to behavioral and cognitive measures. In HU animals that were sham-irradiated or irradiated with 8 Gy, one metabolite was related to behavioral and cognitive measures. In HU animals irradiated with 3 Gy, six metabolites were related to behavioral and cognitive measures. Discussion: These data suggest that it will be possible to develop stable plasma biomarkers of behavioral and cognitive performance, following environmental challenges like HU and radiation exposure.

A compilation of genotoxicity and carcinogenicity data on aromatic aminosulphonic acids

A review is presented to evaluate existing information on genotoxicity and carcinogenicity testing of various aromatic aminosulphonic acids (AASAs). A great variety of water-soluble azo dyes can form aromatic phenyl- or naphthyl-aminosulphonic acids by chemical and enzymatic reduction. AASAs are also used as intermediates in the synthesis of azo dyes and azo pigments and can arise as contaminants in the final products. Comparisons have been made with the data available on the corresponding unsulphonated analogues, some of which are known to be genotoxic and/or carcinogenic. The vast majority of the AASAs were conclusively non-mutagenic in the Ames test. In most cases the absence of genotoxicity was also demonstrated with a variety of other test systems in vitro and in vivo. It is concluded that AASAs, in contrast with some of their unsulphonated analogues, generally have no or very low genotoxic and tumorigenic potential.

Three-generation toxicity study of rats ingesting Brown HT in the diet

Brown HT was fed to rats of both sexes over three generations at dietary concentrations designed to provide daily intakes of 0, 50, 250 and 500 mg Brown HT/kg body weight/day. During the study a number of females died or failed to nurse their litters. This was so severe following the first mating of F1 adults that the animals were remated to provide the next generation. None of these effects were related to treatment. Body weight and food and water intakes were not adversely affected by treatment. No effects of treatment were seen on reproductive performance or foetal and pup development, apart from slight evidence of a treatment-related retarded ossification of the third sternebrae. Organ weights at autopsy showed two changes, one of which was increased kidney weights which, although not present in every generation, seemed to be related to treatment. The other, increased caecum weights, occurred in adult high-dose females of early generations, but not in males or later generations of the study. Apart from brown coloration of tissues, macroscopic and microscopic examination revealed no treatment-related changes. It was concluded that the no-untoward-effect level in the present study was 250 mg Brown HT/kg/day.

Metabolic disposition of 14C-labelled Brown HT in the rat, mouse and guinea-pig

The absorption, metabolism, tissue distribution and excretion of 14C-labelled Brown HT has been studied in the rat, mouse and guinea-pig. Following administration of a single oral dose of either 50 or 250 mg Brown HT/kg, substantially all of the dose was excreted in the urine and faeces within 72 hr, with the majority (more than 80%) being accounted for in the faeces. A significant difference in urinary excretion of radioactivity was seen between male and female rats, as well as clear species differences at the two dose levels used. In all species studied, naphthionic acid was the major urinary metabolite, whereas in the faeces naphthionic acid, trace quantities of unchanged dye and at least two unidentified metabolites were found. Pregnant rats eliminated a single oral dose of 14C-labelled colouring at a rate similar to that in non-pregnant females, but some retention of radioactivity was found in the foetuses. Radioactivity was present in all tissues of male rats 24 hr after an oral dose of 250 mg 14C-labelled Brown HT/kg, with the highest concentrations in the gastro-intestinal tract, kidney and lymph nodes. Clearance from the gastro-intestinal tract was more rapid than from other tissues, but by day 7, the concentration of radioactivity (less than 0.001% of the dose/g) was similar in all tissues except the kidney and mesenteric lymph nodes. Similar results were obtained with animals pretreated for 21 days with either unlabelled or 14C-labelled Brown HT (250 mg/kg/day) prior to a radioactive dose. For most tissues examined, the concentration of radioactivity was greater with pretreatment than without. These results suggest that despite the rapid reduction and elimination of the major part of an oral dose of Brown HT, some colouring and/or metabolites accumulate in most tissues of male rats during repeated daily administration, but that only in the kidney and mesenteric lymph nodes is the accumulation tissue-specific. The accumulated radioactivity is cleared rapidly from most tissues on cessation of treatment. No significant absorption of either Brown HT, metabolites or subsidiary dyes was detected using isolated loops of small intestine.