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Administrative data

basic toxicokinetics in vivo
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Justification for type of information:
The read-across is a category approach based on the hypothesis that compounds in this category are transformed to a common compound. This approach serves to use existing data on genotoxicity, repeated-dose toxicity, and reproductive toxicity endpoints for substances in this category.
There are no relevant variations in properties among source substances and the same potency is predicted for all target substances. This is Scenario 5 of the RAAF . Substances ATG, MEATG, KTG, CaTG, and NaTG are different inorganic salts of a common acid, thioglycolic acid (TGA; synonym: 2- mercaptoacetic acid). They dissociate rapidly in aqueous media, e.g., the test organism, to the common thioglycolate anion and to their different counter ions. The water solubility of all category members is high, except for CaTG which is only moderately soluble in water.
In the repeated-dose toxicity studies with NaTG, specific toxicity is exerted via the well-investigated inhibition of mitochondrial fatty acid beta-oxidation by the thioglycolate (2-mercaptoacetate) anion 2,3,4. Inhibition of beta-oxidation leads to increased triglycerides and decreased acetyl-CoA in liver, and subsequently reduced gluconeogenesis. The latter presents as hypoglycaemia in NaTGtreated rats, which is aggravated by fasting (Grosdidier, 2011; Report No. 37043 TSR). This mode of action (MoA) is thought to mediate the acute oral toxicity in fasted rats observed with all category members.
It can be predicted with high confidence that the target substances will display the same MoA and lead to the same effects seen with NaTG.
For more detailed information please refer to section 13.2.
Reason / purpose for cross-reference:
read-across: supporting information

Data source

Materials and methods

Test material

Constituent 1
Chemical structure
Reference substance name:
(2-hydroxyethyl)ammonium mercaptoacetate
EC Number:
EC Name:
(2-hydroxyethyl)ammonium mercaptoacetate
Cas Number:
Molecular formula:
2-hydroxyethan-1-aminium 2-sulfanylacetate

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
Study A: 0.27% of the applied dose
Study B: 0.24% of the applied dose
Study C: 0.26% of the applied dose
Details on excretion:
Urine: 76.5 - 80.3% of the eliminated 14C
Faeces: 19.7 - 23.5% of the eliminated 14C

Metabolite characterisation studies

Metabolites identified:
not measured

Applicant's summary and conclusion

Based on the data for ATG, MeaTG is assumed to show low dermal absorption and no potential for bioaccumulation.