2-mercaptoethanol

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

THE METABOLISM OF MERCAPTOETHANOL BY THE LIVING RAT

Author:

G. Federici, G. Ricci, S. Dupre, A. Antonucci, D. Cavallini

Year:

1976

Bibliographic source:

Biochemistry and Experimental Biology, 12, 341-345

Materials and methods

Objective of study:

absorption

excretion

metabolism

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

investigation on the possible role of mercaptoethanol as a precursor of other sulfur·containing compounds in the living animal

GLP compliance:

no

Test material

Test material information

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

no data

Sex:

male

Details on test animals or test system and environmental conditions:

no data

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

not specified

Details on exposure:

single administration of 0.4 mCi of 35S-mercaptoethanol

Duration and frequency of treatment / exposure:

single administration

Doses / concentrations

Dose / conc.:

0.4 other: mCi

No. of animals per sex per dose / concentration:

2

Control animals:

no

Positive control reference chemical:

not applicable

Details on study design:

Male rats of the Wistar strain (150-200 g) received 35 S·Mercaptoethanol (0.4 mCi/mmol) by intraperitoneal injection. They were kept in metabolic cages on a conventional complete diet.

Details on dosing and sampling:

Urine was collected daily, separated from feces, in a vessel containing few drops of concentrated HCI and stored frozen unless analyzed immediately.

Statistics:

not applicable

Results and discussion

Any other information on results incl. tables

Total radioactivity registered in the urine after injection of 0.4 mCi of ³⁵S-mercaptoethanol was 91% in the first day and 8% in the second day. Within three days almost all the radioactivity injected was excreted in the urine. The results clearly indicate that mercaptoethanol is largely metabolized by the living rat up to the conversion into sulfate. A number of other metabolites have also been detected but not identified. Electrophoretic and chromatographic analysis, in various conditions, led to the identification of sulphate as a major component and small amount of isethionic acid. The presence of mixed disulfides of injected mercaptoethanol with naturally occurring sulphydryl compounds present in the urine and the presence of radioactive S-sulfonates (Bunte salts) should be excluded by the negative results obtained by oxidation and reduction of the urine. The absence of mixed disulfides and of Bunte salts has been confirmed by treating the urine with an excess of unlabelled mercaptoethanol. HCl hydrolysis indicated that none of the peaks should be imputable to a sulfate ester.

Applicant's summary and conclusion

Conclusions:

35 S-Mercaptoethanol injected into living rats is rapidly metabolized, giving raise to at least five compounds, which are excreted in the urine. After two days 99% of injected radioactivity is recovered. Electrophoretic and chromatographic analysis, in various conditions, led to the identification of sulphate as a major component and small amount of isethionic acid. The remaining metabolites were not identified.