Ethyl acrylate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Objective of study:

other: Metabolism rate, Km and Vmax determinations

Principles of method if other than guideline:

- Principle of test:
This study was conducted to investigate in vitro hydrolysis and glutathione conjugation rates of ethyl acrylate (EA). Ethyl Acrylate was part of a group of materials chosen for initial experimental determination of metabolism rates in rat liver microsomes and whole rat blood at a single substrate concentration (500 μM). Additionally, Km and Vmax determinations were made by performing incubations utilizing various concentrations (32.25, 62.5, 125, 250, and 500 μM) and a single rat liver microsomal protein concentration of 0.1 mg/mL or 0.5 mg/mL. After rates were determined, a third set of incubations were performed to evaluate the ability of the acrylate to conjugate with glutathione in the presence of glutathione transferases (GST).

Short description of test conditions:
This study was conducted in two stages. The first stage (Stage I) comprised of test material incubation in two different matrices, either liver microsomes or whole blood from F344 rats. Whole blood was obtained from Bioreclamation, LLC (Hicksville, New York, USA) and liver microsomes were obtained from Sekisui Xenotech, LCC (Kansas City, Kansas, USA). The second phase of the study (Stage II) explored glutathione activity via incubation of the test material with tritiated glutathione/glutathione in the presence of glutathione transferase with subsequent chemical analysis.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ethyl acrylate

EC Number:

205-438-8

EC Name:

Ethyl acrylate

Cas Number:

140-88-5

Molecular formula:

C5H8O2

IUPAC Name:

ethyl acrylate

Specific details on test material used for the study:

Chemical Name: 2-Propenoic acid ethyl ester
Synonyms: Acrylic acid ethyl ester
Lot/Reference/Batch Number: A829H7K000
Purity/Characterization (Method of Analysis and Reference): The non-GLP purity of the test material was determined to be 99.9 wt% (The Dow Chemical Company, 2017a).
Test Material Stability Under Storage Conditions: The test material EA, lot A829H7K000, was not tested for neat test material
stability.
Molecular Formula: C5H8O2
Molecular Weight: 100.1
CAS Number: 140-88-5

Administration / exposure

Statistics:

Descriptive statistics were used, i.e., mean ± standard deviation, or relative standard deviation (standard deviation/mean). All calculations were conducted using Microsoft Excel spreadsheets in full precision mode (15 digits of accuracy). The half-life values of the acrylates and the rates of hydrolysis to AA for the nine acrylates in whole rat blood and rat liver microsomes in Stage IA were determined using GraphPad Prism version 5.03 (GraphPad Software, La Jolla, CA, USA). The percent remaining of the parent esters were fit to one-phase exponential decay curves to determine ke (min^-1) and Clint (μL/min/mg). Calculation of Km and Vmax for the AA formation from acrylate in rat liver microsmes (Stage IB) was also performed using GraphPad Prism v5.03 according to the Michaelis-Menten Kinetic Model.

Results and discussion

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

In rat liver microsomes, Ethyl Acrylate hydrolyzed to form the metabolite acrylic acid (AA) with a half-life of less than 2 minutes. In whole rat blood, Ethyl Acrylate rapidly metabolized, shown by a significant and (nearly) complete loss of the parent acrylate. Based on the measured concentrations of the remaning parent acrylates, the half-life values for Ethyl Acrylate was less than 3 minutes in rat blood. Ethyl Acrylate formed a single GSH conjugate in the presence of GST.

Any other information on results incl. tables

Ethyl Acrylate (EA) was chosen for initial experimental determination of metabolism rates in rat liver microsomes and whole rat blood at a single substrate concentration (500 μM). Additionally, Km and Vmax determinations were made by performing incubations utilizing various concentrations (31.25, 62.5, 125, 250, and 500 μM) and a single rat liver microsomal protein

concentration of 0.1 mg/mL or 0.5 mg/mL. After rates were determined, a third set of incubations were performed to evaluate the ability of each acrylate to conjugate with glutathione in the presence of glutathione transferases (GST).

In rat liver microsomes, EA hydrolyzed to form the metabolite acrylic acid (AA). EA has a half-life of less than 8.5 minutes.

In whole rat blood, EA is rapidly metabolized, shown by a significant and (nearly) complete loss of the parent acrylate. However, unlike the rat liver microsomal incubations, the concentrations of the formed AA were significantly lower. Based on the measured concentrations of the remaning parent acrylates, the half-life values for all acrylates were less than 12 minutes in rat blood.

In the serial substrate concentrations (31.25, 62.5, 125, 250, and 500 μM) of EA, further experiments were conducted to determine Km and Vmax values for acrylate ester hydrolysis to AA in rat liver microsomes.

EA formed a single GSH conjugate in the presence of GST. The rate of formation of these GSH conjugate was 2.19 nmol/mg protein/min.

Overall, these in vitro metabolism results imply that EA can be quickly metabolized through hydrolysis to AA and/or glutathione conjugation in vivo.

Applicant's summary and conclusion

Conclusions:

In rat liver microsomes, EA hydrolyzed to form the metabolite acrylic acid (AA). EA has a half-life of less than 2 minutes.
In whole rat blood, EA is rapidly metabolized, shown by a significant and (nearly) complete loss of the parent acrylate. However, unlike the rat liver microsomal incubations, the concentrations of the formed AA were significantly lower. Based on the measured concentrations of the remaning parent acrylates, the half-life values for all acrylates were less than 3 minutes in rat blood.
In the serial substrate concentrations (31.25, 62.5, 125, 250, and 500 μM) of EA, further experiments were conducted to determine Km and Vmax values for acrylate ester hydrolysis to AA in rat liver microsomes.
EA formed a single GSH conjugate in the presence of GST. The rate of formation of these GSH conjugate was 2.19 nmol/mg protein/min.
Overall, these in vitro metabolism results imply that EA can be quickly metabolized through hydrolysis to AA and/or glutathione conjugation in vivo.

Executive summary:

This study was conducted to investigate in vitro hydrolysis and glutathione conjugation rates of Ethyl Acrylate (EA). EA was chosen for initial experimental determination of metabolism rates in rat liver microsomes and whole rat blood at a single substrate concentration (500 μM). Additionally, Km and Vmax determinations were made by performing incubations utilizing various concentrations (31.25, 62.5, 125, 250, and 500 μM) and a single rat liver microsomal protein concentration of 0.1 mg/mL or 0.5 mg/mL. After rates were determined, a third set of incubations were performed to evaluate the ability of each acrylate to conjugate with glutathione in the presence of glutathione transferases (GST).

In rat liver microsomes, EA hydrolyzed to form the metabolite acrylic acid (AA). EA has a half-life of less than 2 minutes.

In whole rat blood, EA is rapidly metabolized, shown by a significant and (nearly) complete loss of the parent acrylate. However, unlike the rat liver microsomal incubations, the concentrations of the formed AA were significantly lower. Based on the measured concentrations of the remaning parent acrylates, the half-life values for all acrylates were less than 3 minutes in rat blood.

In the serial substrate concentrations (31.25, 62.5, 125, 250, and 500 μM) of EA, further experiments were conducted to determine Km and Vmax values for acrylate ester hydrolysis to AA in rat liver microsomes.

EA formed a single GSH conjugate in the presence of GST. The rate of formation of these GSH conjugate was 2.19 nmol/mg protein/min.

Overall, these in vitro metabolism results imply that EA can be quickly metabolized through hydrolysis to AA and/or glutathione conjugation in vivo.