N,N-Diethylacrylamide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

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 DISTRIBUTION AND METABOLISM OF ACRYLAMIDE AND ITS NEUROTOXIC ANALOGUES IN RATS

Author:

Edwards PM

Year:

1975

Bibliographic source:

Biochemical Pharmacology, Vol. 24, pages 1277-1282

Report date:

1975

Materials and methods

Objective of study:

distribution

metabolism

Test guideline

Qualifier:

no guideline followed

Test material

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

other: Porton

Sex:

male

Details on test animals or test system and environmental conditions:

Body weight: 200 + 20 g

Administration / exposure

Route of administration:

intravenous

Vehicle:

other: 60% m-dioxan-5-ol in water

Details on exposure:

(176 mg/kg) were given intravenously in 60% m-dioxan-5-ol in water. The volume of each solution injected was 1 mL/kg.

Duration and frequency of treatment / exposure:

Single intravenous dose

Doses / concentrations

Dose / conc.:

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

Details on dosing and sampling:

- Detection of acrylic amides: paper chromatograms
- Assay of free acrylamide and N-hydroxymethylacrylamide in blood: Rats were aesthetized with ether and 2 mL blood removed from the posterior vena cava into a heparinized syringe. Blood (1 mL) was mixed with 3 mL methanol containing Tris(hydroxymethyl)-aminomethane (0.1% w/v). The clear supernatant obtained after centrifugation of the extract in a bench centrifuge for 15 min was assayed.
- Paper chromatography of blood extracts: Samples (100µL) were applied to Whatman No. 1 chromatography paper. Papers were developed by descending chromatography for 16 hr at 25 ° using 60mL butanol saturated with water.
- Assay of free glutathione in the liver: All rats were starved from the time of dosing until the livers were removed in order to avoid any effect of changes in food consumption on liver glutathione. The livers were homogenized in 11 vol. buffered ethanol. The homogenate was centrifuged at 2500 g for 20 min and the supernatant assayed for glutathione.
- Identification of the glutathione conjugates of acrylamide and N-hydroxymethylacrylamide in extracts of liver and bile: Ethanolic extracts of liver were applied to Whatman No.1 chromatography paper after concentration by rotary evaporation. Bile was collected by cannulation of the bile duct close to the duodenum and applied directly to Whatman No. 1 chromatography paper.
- Separation of the glutathione conjugates of acrylamide and N-hydroxymethylacrylamide from bile by ion-exchange chromatography: Bile (1.5 mL) was applied directly to ion-exchange columns (15.5 x 0.9 cm) of acetate resin and washed on with 1 mL water. The column was eluted with 120mL 0.1 N acetic acid followed by 0.22 N acetic acid. The glutathione conjugates of acrylamide eluted in the same volume, between 120 and 190mL. The concentration of glutathione conjugates in the eluate was assayed with ninhydrin.
- Estimation of specific radioactivity of glutathione conjugates: The radioactivity was measured by scintillation counting in Instagel. Efficiency of counting was estimated by internal standardization. The chemical and radiochemical purity of all fractions was checked by paper chromatography.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:

- Concentration of acrylamide and N-hydroxymethylacrylamide in blood after intravenous dosing: The blood concentrations fell exponentially after intravenous dosing. The half-life for test item is 1.55 hr. Extrapolation of the decay curve back to zero time gives a concentration very close to the theoretical value for dilution in total body water.
- Identification of acrylamide in the blood of rats dosed with acrylamide analogues: Chromatography of methanolic extracts of blood of rats 0.5 and 1 hr after dosing rats with either N-methylacrylamide or test item indicated that neither acrylamide nor N-hydroxymethylacrylamide had been formed. A 5 percent molar conversion to acrylamide or N-hydroxymethylacrylamide could have been detected.

Metabolite characterisation studies

Details on metabolites:

- Concentration of glutathione in the liver after dosing: The liver glutathione fell rapidly, reaching a minimum of about 36 per cent normal values between 2 and 4 hr, then returned to normal, or slightly higher than normal concentration by 24 hr. There was little diurnal variation even in fed rats. Dosing causes a loss of glutathione from the liver. The reaction products of test item with liver glutathione are very rapidly excreted in the bile.

Applicant's summary and conclusion

Conclusions:

Test item distributed throughout total body water within a few minutes. The concentrations of compound decreased exponentially after this initial distribution, with a half-life of less than 2 hr. The compound caused a rapid decrease in liver glutathione in vivo, and the glutathione conjugates were excreted in the bile.