Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not applicable
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-study similar to OECD guideline 417.
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1986
Report date:
1986

Materials and methods

Objective of study:
other: metabolism and disposition
Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 417 (Toxicokinetics)
Principles of method if other than guideline:
No data
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Ethyl 3-ethoxypropionate (EEP, EK Accession #906315, SRID # X-18626-184-7) was obtained from Eastman Chemical Products, Inc. (Kingsport, TN). A sample of EEP was analyzed by gas chromatography-mass spectrometry (gc-ms) and determined to be between 99.7% and 99.9% pure.

[Propionyl-2-14C]EEP was obtained from New England Nuclear (Boston, MA) with a specific radioactivity of 0.725 mCi/mole. 14C-EEP in this
preparation accounted for 97.0% of the radioactivity, as determined by gas chromatography (gc) with radiochemical detection.
Radiolabelling:
yes
Remarks:
[Propionyl-2-14Cl]EEP was obtained from New England Nuclear (Boston, MA) with a specific radioactivity of 0.725 mCi/mole. 14C-EEP in this preparation accounted for 97.0% of the radioactivity, as determined by gas chromatography (gc) with radiochemical det

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories (Wilmington, MA)
- Weight at study initiation: between 200 g and 250 g
- Fasting period before study: Fasted for a 4 hour period immediately after dosing.
- Housing: no data
- Individual metabolism cages: yes
- Diet:ad libitum
- Water: ad libitum
- Acclimation period: at least one day


ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light):no data

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: Dose solutions were prepared by mixing the 14C-EEP with unlabelled EEP such that each dose level contained approximately 20 µCi.
Details on exposure:
Oral Gavage Dosing
The dose solutions were prepared by mixing the 14C-EEP with unlabelled EEP such that each dose level contained approximately 20 µCi. Groups of
5 rats were administered 14C-EEP through a stainless steel oral gavage needle at dose levels of 150 mg/kg or 1500 mg/kg. The animals were placed in glass metabolism cages (Wetabowl®, Jencons Ltd., Hemel Hempstead, Herts., England) immediately after dosing.
Duration and frequency of treatment / exposure:
Single oral dose
Doses / concentrations
Remarks:
Doses / Concentrations:
150 and 1500 mg/kg
No. of animals per sex per dose / concentration:
Five
Control animals:
no
Positive control reference chemical:
not applicable
Details on study design:
Groups of 5 male Sprague-Dawley [CW-(SD)BRl rats weighing 200 g to 250 g were administered [propionyl-2-14C-EEP (14C-EEP) by oral gavage at dose levels of 150 mg/kg or 1500 mg/kg. Urine, feces and expired air were collected at intervals for 144 hours. Tissues were collected at autopsy. Urinary metabolites were separated using a Waters hplc system with a reversed phase (C-18) column and a mobile phase of aqueous formic acid and acetonitrile. Radioactively labelled components were detected using a radioactivity monitor.
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, expired air, cage washes
- Time and frequency of sampling: at interals up to 144 hours



METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces, tissues, cage washes, bile
- Time and frequency of sampling: 24 hours
- From how many animals: samples pooled from each of the two dose groups
- Method type(s) for identification: GC/MS, HPLC, RID
- Limits of detection and quantification:

Results and discussion

Preliminary studies:
Not applicable

Toxicokinetic / pharmacokinetic studies

Details on absorption:
Absorption of 14C-EEP from the gastrointestinal tract was rapid following oral gavage administration of a single 150 mg/kg or 1500 mg/kg dose to male rats.
Details on distribution in tissues:
Recovery of the 14C after 144 hours was essentially complete, averaging 95.4% (±1.7%) for the 150 mg/kg dose group and 102.5% (±1.8%) for the 1500 mg/kg dose group. Only about 1% of each dose was recovered in the tissues and about 4% in the carcasses at 144 hours. No evidence was found for the concentration of 14C in any tissue or organ. The 14C remaining in the tissues and carcass may have been incorporated into tissues through the normal intermediary biochemical processes by a sequence similar to that described earlier for the generation of
14CO2 3-Hydroxypropionic acid is a normally occurring biochemical, the carbons of which may be incorporated into amino acids and, through
oxidation to acetyl coenzyme A, to lipids. Malonic acid, as its coenzyme A derivative, is a precursor for both the de novo synthesis and
elongation of fatty acids. This possibility is supported by the observation that, after 24 hours (lower dose) or 48 hours (higher dose),
the amount of 14C eliminated in the expired air was greater than that excreted in the urine and most of the remaining dose of 14C-EEP was
eliminated as 14CO2. This may be an indication that the 14C incorporated into the tissues is turning over and releasing 14CO2.
Details on excretion:
Radioactivity was eliminated in the urine rapidly after a single oral gavage dose of 14C-EEP of 150 mg/kg or 1500 mg/kg. At the 150 mg/kg dose level, a mean of 34.3% of the dose was excreted in the urine within 8 hours and a mean of 50.0% of the dose was excreted by 24 hours after administration. At the 1500 mg/kg dose level, means of 17.7% and 65.0% of the dose were excreted in the urine within 8 hours and 24 hours after administration, respectively. Only small amounts of 14C were detected in the urine between 24 and 144 hours (approximately 1.5% for the lower dose group and approximately 6.5% for the higher dose group animals) .

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
Monoethyl malonate was detected in the urine of rats from both dose groups. This metabolite was hydrolyzed by aryl sulfatase and by
1.5 N-HCl to produce malonic acid. Small amounts of malonic acid (2-5% of each dose) were detected in the urine also. This metabolite was probably derived from monoethyl malonate either biologically or as an artifact during sample preparation. Authentic monoethyl malonate was
demonstrated to hydrolyze to malonic acid on incubation with aryl sulfatase or 1.5 N-HCl. The identification of monoethyl malonate as a
major metabolite of EEP is surprising. This metabolite is presumed to have been formed by the oxidation of the 3-carbon of ethyl 3-hydroxypropionate, indicating that microsomal oxidative dealkylation of the ethyl ether moiety occurred in preference to simple hydrolysis of the ester by blood or tissue esterases.

Only trace amounts (< 2% of the dose) of the parent compound were detected in the urine at either dose level. The relative amounts of the
major urinary metabolites were dependent upon the dose. After a dose of 150 mg/kg of 14C-EEP, the major urinary metabolite was ethyl malonate,
which accounted for more than half of the urinary radioactivity in the first 24 hours (about 29% of the dose). Halonic acid in the urine
accounted for an additional 5% of the dose. 3-Ethoxypropionic acid and its glycine conjugate accounted for about 14% of the dose. After a dose
of 1500 mg/kg, 3-ethoxypropionic acid and its glycine conjugate accounted for about 44% of the dose, compared with less than 17% of the dose
attributable to ethyl malonate and malonic acid. It appears, therefore, that the microsomal 0-dealkylation of EEP became saturated at the higher dose, resulting in an increased rate of hydrolysis of the ester moiety and elimination of 3-ethoxypropionic acid rather than ethyl malonate.

Any other information on results incl. tables

Ethyl 3-ethoxypropionate (EEP) was rapidly absorbed, metabolized and excreted by male rats following oral gavage administration of doses of 150 or 1500 mg/kg. A substantial proportion of each dose was eliminated as CO2, indicating that the molecule was completely oxidized. The majority of the remaining portion of each dose was eliminated in the urine within 24 hours of dosing. The major urinary metabolites were ethoxypropionic acid, the monoethyl ester of malonic acid and the glycine conjugate of 3-ethoxypropionic acid. No evidence was found for the production of alkoxyacetic acid metabolites, such as those produced by the metabolism of some low molecular weight ethylene glycol ethers.These metabolic data are consistent with the low acute toxicity of EEP.

Applicant's summary and conclusion

Conclusions:
Absorption of 14C-EEP from the gastrointestinal tract was rapid following oral gavage administration of a single 150 mg/kg or 1500 mg/kg dose to male rats. About 2-3% of each dose was recovered in the feces by 72 hours, demonstrating that absorption was essentially complete. Most of the fecal 14C was not extractable with water or acetone, suggesting that it was not parent compound.
Executive summary:

A study was conducted to determine the metabolic fate and disposition of EEP in male rats following a single oral gavage administration. Groups of 5 male Sprague-Dawley [CW-(SD)BRl rats weighing 200 g to 250 g were administered [propionyl-2-l4C-EEP (14C-EEP) by oral gavage at dose levels of 150 m/kg or 1500 mg/kg. Urine, feces and expired air were collected at intervals for 144 hours. Tissues were collected at autopsy. Urinary metabolites were separated using a Waters HPLC system with a reversed phase (C-18) column and a mobile phase of aqueous formic acid and acetonitrile. Radioactively labelled components were detected using a radioactivity monitor. Radioactivity was rapidly eliminated in the breath and urine after each dose of 14C-EEP. At the 150 mg/kg dose level, 34.3% and 50.0% of the 14C was excreted in the urine within 8 and 24 hours of dosing, respectively. At the 1500 mg/kg dose level, 17.7% and 65.0% of the 14C was excreted in the urine within 8 hours and 24 hours of dosing, respectively. After 24 hours, only an additional 1.5% and 6.5% of the low and high dose, respectively, was detected in the urine. About 2% of each dose was found in the feces, mostly in the first 24 hours. About 34.5% and 20.0% of the low and high

dose, respectively, was recovered as 14CO2, mostly in the first 24 hours. volatile organic materials accounted for < 0.4% of the dose

by 144 hours. About 1% of the administered radioactivity was recovered from the tissues and about 4% from the carcasses of the animals receiving 150 mg/kg or 1500 mg/kg doses of 14C-EEP. The major urinary metabolites of EEP were monoethyl malonate (30% nd 17% of the low and high dose, respectively) and 3-ethoxypropionic acid (8% and 41% of the low and high dose, respectively). Other metabolites included malonic acid and the glycine conjugate of 3-ethoxypropionic acid. Trace amounts of 14C-EEP were detected after both doses. Recovery of 14C after 144 hours was essentially complete, averaging 95.4% ( ±1.7%) and 102.5% ( ±1.8%) for the low and high dose group, respectively. No evidence was found for the production of alkoxyacetic aci metabolited, such as those produced by the metabolism of some low moleculr weight ethylene glycol ethers.