m-bis(2,3-epoxypropoxy)benzene

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics, other

Remarks:

in vivo and in vitro

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Objective of study:

metabolism

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

Enzyme kinetics: Alkylating activity was estimated according to the procedure of Friedman and Boger; the test solution was reacted at 100°C with 0.4 mL of a 5% acetone solution of 4-(4'-nitrobenzyl)pyridine (NBP) in 3 mL acetate buffer (pH 4.6) for 20 min. After cooling 5 mL ethylacetate and 1 mL 2 N sodium hydroxide was added, the mixture was shaken vigorously, centrifuged and the light absorbance of the upper organic phase was measured immediately at 540 nm.
Liver homogenate postmitochondrial supernatant (S-9) was prepared from either uninduced mice or from induced rats; enzyme induction in the latter case was by the combination treatment of beta-naphthoflavone and phenobarbital. For the experiments, the S-9 was diluted to the desired concentration with phosphate buffered saline (PBS). The determination of the protein content was performed by Lowry analysis. The measurements of enzyme kinetics were conducted in the following way: 50 µL of a DMSO-solution of the various test compounds was incubated with 1 ml S-9 for 10 min at 37°C, yielding final concentrations of 5-100 µg/mL for RDGE and 20-100 µg/mL for the two diol-epoxides. At the end of the incubation period the enzymatic reaction was stopped by the addition of a threefold excess of ice-cold acetone. After centrifugation the supernatant was assayed for alkylating activity by the NBP-procedure. The difference between the absorbance values before and after incubation was then used in the calculation of the kinetic parameters. Time-course experiments were performed in the same way with the reaction stopped at various times after the addition of S-9; the metabolites produced by S-9 were also isolated in this manner, namely by acetone precipitation of proteins, centrifugation and subsequent concentration of the supernatant. Judging from the absorbance values obtained with these compounds either in the presence or in the absence of S-9, the recoveries of parent compounds and metabolites, respectively, obtained with this procedure were between 90% and 100%.
Metabolism kinetics: Male and female ICR-mice were given the test compound by gavage. The animals were kept in metabolic cages, where they had access to water only during the experiment. Urine and faeces were collected for 1-4 h. Urinary metabolites were then extracted either by ethylacetate at pH 7 and pH 2, or by XAD-2 adsorption. Analysis of urinary and S-9 metabolites was by thin-layer chromatography on silica gel plates in acetone/hexane (1:1) as the most suitable solvent system.

GLP compliance:

no

Specific details on test material used for the study:

Resorcinol diglycidyl ether (RDGE) was obtained by reacting an about 4-fold excess of epichlorohydrin with the aromatic compound, resorcinol. After a few hours of stirring at an elevated temperature an exact equivalent of sodium hydroxide was added slowly to this solution. Purification was then by vacuum distillation. In the same manner the 14C-labelled compound used in this study, namely [14C] resorcinol diglycidyl ether (R*DGE), resorcinol di-[14C]glycidyl ether (RDG*E), were synthesized from the appropriately 14C-labelled precursor substances, which were obtained from Amersham (Amersham, U.K.). The presumed bis-diol and diol-epoxide metabolites were also synthesized in an analogous manner by the reaction of resorcinol with glycidylglycerine alone, or in combination with epichlorohydrin, in this case followed by the sodium hydroxide addition.

Radiolabelling:

yes

Species:

mouse

Strain:

ICR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Institute of Animal Husbandry (University of Zurich)
- Housing: metabolic cages
- Water: access only during the experiment

Route of administration:

oral: gavage

Vehicle:

DMSO

Remarks:

10% aqueous DMSO

Duration and frequency of treatment / exposure:

once

Dose / conc.:

500 mg/kg bw/day (actual dose received)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Control animals:

no

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY
- Tissues and body fluids sampled: urine, faeces
- Time and frequency of sampling: 60, 120 and 240 min


METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: tissues (liver homogenate postmitochondrial supernatant S-9)
- From how many animals: from uninduced mice or from induced rats
- Method type(s) for identification: TLC combined with light absorbance at 540 nm
- Limits of detection and quantification: NA

Type:

metabolism

Results:

RDGE seems to become fully detoxified during its passage through the organism

Details on excretion:

4 hours after RGDE gavage at 1000 mg/kg, 46.8% of applied dose was recovered from urine.

Key result

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 6 min

Remarks:

apparent half-life of RDGE metabolism

Metabolites identified:

yes

Details on metabolites:

Urinary metabolites (% of amount applied to thin-layer plate): bis-diol (64%), unidentified polar conjugates (21%) and phenol-diol (4%)

Various concentrations of RDGE, as well as of this respective diol-epoxide derivatives were incubated for ten minutes and the respective maximal reaction velocities and the Michaelis-Menten constants of these compounds were estimated by means of Lineweaver-Burk plots.

Kinetic paremeters for the enzymatic inacivation of RDGE

Metabolite	Km(apparent)		Vmax(apparent) E540/min/mg protein
	µg substrate/mL	nM/mL
RDGE               Bis-epoxide               Diol-epoxide	140 42	630 175	90 55

Conclusions:

The degradation of the reactive epoxide groups in RDGE to the bis-diol occurs as a continuous process. The compound binds to the enzyme and both glycidyl residues are converted sequentially to the bis-diol.

Description of key information

No experimental toxico-kinetic data are available for assessing adsorption, distribution and excretion of the substance. Based on effects seen in the human health toxicity studies and physico-chemical parameters The substance is expected to be readily absorbed via the oral and inhalation route and somewhat lower via the dermal route. Using the precautionary principle for route to route extrapolation the final absorption percentages derived are: 50% oral absorption, 50% dermal absorption and 100% inhalation absorption.

The metabolism is described in the robust study summary of Basic toxicokinetics.

Key value for chemical safety assessment

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

Present the text of the toxico-kinetic assessment here and add the file to this endpoint summary

No bioaccumulation is < 500, Low is < 2000 and high is > 2000