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Endpoint:
dermal absorption in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 427 (Skin Absorption: In Vivo Method)
Qualifier:
equivalent or similar to
Guideline:
other: OECD TG 417
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h
Type of coverage:
occlusive
Vehicle:
water
Duration of exposure:
48 hr exposure
Doses:
12.5 mg/kg bw (corresponding to 15-20 µCi of radioactivity)
No. of animals per group:
4
Control animals:
no
Details on study design:
TEST SITE
- Area of exposure: interscapularly and as far anteriorly on the back as possible, 4 cm2
- Type of wrap if used: Immediately after dosing, the dosed area was covered with a piece of teflon@ film (4 cm X 4 cm) which was secured to the Stomahesive patch/well with surgical adhesive. The dosed area was then wrapped with veterinary bandaging tape.
- Time intervals for shavings or clipplings: before exposure
Signs and symptoms of toxicity:
no effects
Dermal irritation:
no effects
Absorption in different matrices:
- Skin test site: 32.80 ± 6.16 %
- Carcass: 9.19 ± 0.93 %
- Urine: 27.38 ± 3.06 %
- Cage wash: 0.70 ± 0.28 %
- Faeces: 0.59 ± 0.41 %
- Expired air: 26.53 ± 2.73 % (CO2) + 0.36 ± 0.45 % (volatile organics)
Total recovery:
- Total recovery: 97.54 ± 1.06 %
Key result
Dose:
12.5 mg/kg bw
Parameter:
percentage
Absorption:
ca. 66 %
Remarks on result:
other: 48 hr
Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Objective of study:
toxicokinetics
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Qualifier:
equivalent or similar to
Guideline:
other: OECD TG 427
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h
Route of administration:
dermal
Vehicle:
water
Details on exposure:
TEST SITE
- Area of exposure: interscapularly and as far anteriorly on the back as possible, 4 cm2
- Type of wrap if used: Immediately after dosing, the dosed area was covered with a piece of teflon@ film (4 an X 4 an) which was secured to the Stomahesive patch/well with surgical adhesive. The dosed area was then wrapped with veterinary bandaging tape.
- Time intervals for shavings or clipplings: before exposure


Duration and frequency of treatment / exposure:
48 hr exposure
Dose / conc.:
12.5 mg/kg bw/day
Remarks:
corresponding to 15-20 µCi of radioactivity
No. of animals per sex per dose:
4
Control animals:
no
Details on study design:
After administration or termination of exposure to 14C-HEA, rats from all groups were housed in glass Roth-type metabolism cages. All urine, cage rinse, and feces were collected at specified intervals for up to 48 hr post-dosing or post-exposure and analyzed for radioactivity. In addition, expired organics and 14CO2 were trapped for the 48 hr post-dosing or post-exposure period. Selected samples of urine were analyzed by high performance liquid chromatography (HPLC) to determine 14C metabolic profiles.
The rats were sacrificed 48 hr after administration or exposure to 14C-HEA, and the radioactivity remaining in samples of blood, skin, and the carcass was quantified. For the dermal route of administration, the radioactivity associated with the skin at the dosed site was also determined. in order to determine blood concentration-time profiles, separate groups of animals (different from the groups used to determine the disposition of HEA) were utilized so that expired 14CO2 would not be lost while blood was collected from the animals in the Roth cages.
Radioactivity was quantified with a Beckman LS 3801 or Beckman LS 9000 liquid scintillation Counter (Beckman Instrument Inc., Fullerton, CA).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum, cage washes, bile, 14CO2
- Time and frequency of sampling:
urine (0-12, 12-24 and 24-48 hr post-dosing), faeces (at 24 hr intervals), 14CO2 (0.25, 0.5, 1, 2, 4, 8, and 12 hr post-exposure) (trapped in a mixture of CO2 trapping solution (monoethanolamine: methoxy-2-propanol, 3:7, v/v) and combustion scintillant (Spectrafluor@:methoxy-2-propanol:toluene 12:22:66, v/v)
Blood samples (100 µL) for the 14C plasma and red blood cell time-couse determinations were collected at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 30 and 48 hr after the administration of 14C-HEA by the dermal route.
Statistics:
The half-lives for the CO2 excretion and the plasma radioactivity were determined from the slope of the line obtained by regression analysis of the excretion time-course obtained from each treatment group. Statistical analysis of the data was limited to the calculation of means and standard deviations where appropriate. Pharmacokinetic analysis (calculation of half-lives, AUC's etc.) were carried out using standard methodologies.
Details on distribution in tissues:
For the dermal route of administration, about 33 % of the applied dose recovered was associated with the skin or materials used for restricting access to the dermal dose site. Of this 33 %, 11 % of the applied radioactivity was associated with the dosed skin and the remaining 22 % was recovered in the components of the bandage (Stomahesive patch/well, which defined the dosed site, Teflon@ cover and VetRap@). Nine percent of the dose was found in the tissues and carcass.
Details on excretion:
For the dermal route of administration, 27 % of the radioactivity was recovered in the urine and a similar amount of 27 % was recovered as 14CO2. Less than 1 % of the dose was found as volatile organics in the expired air and in the final cage wash and only 0.6 % of the dose was recovered in the faeces.
Following dermal application, nonquantifiable levels of 14CO2 were observed for up to one half hour post application. In addition, there was a lag in peak 14CO2 excretion as compared to the oral and ip routes of administration. This peak occurred at the 12-24 hr collection interval. By 12 hr post-dosing, only 13 % of the dose had been eliminated as 14CO2 in the expired air. The exhalation of 14CO2 derived from 14C-HEA appeared to follow first-order kinetics as a biphasic process, except following dermal administration.
For the dermal route of administration, 38 % of the total radioactivity excreted via the urine was excreted during the 0-12 hr interval and about the same percentage was excreted in the 12-24 hr collection interval.
Metabolites identified:
yes
Details on metabolites:
HPLC analyses were performed on pooled urine specimens from all treatment groups. Recovery from the HPLC System ranged from 90% to 114%. For all treatment groups, the radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

The average 14C-HEA doses (mg/kg bw) administered to the dermal treatment group ranged from 84 % to 107 % of target.

No signs of toxicity were observed following dermal administration. In addition, at 48 hr post-dermal application there was an absence of skin irritation.

Since an average of only 66 % of the applied dermal dose was absorbed within 48 hr post-dosing, the dermal absorption of 14C-HEA was a relatively slow process.

The data show, that once systemically available, HEA is rapidly metabolized and eliminated from the body.

Half-lives:

Following the 12.5 mg/kg dermal dose, the half-life for the terminal phase of elimination via 14CO2 was determined to be approximately 17 hr. The half-life for the initial phase of elimination was 4.9.

For the dermal route of administration the half-life of elimination in the urine was approximately 14 hr.

The blood concentration-time profile following dermal administration showed a slow rise in 14C blood concentrations from 15 min post-dosing to peak at 12 hr postdosing, suggesting a slow rate of dermal absorption. However, following dermal absorption the plasma radioactivity concentration-time profile was monophasic suggesting a first order process of elimination. The terminal half-life for the disappearance of plasma 14C activity following dermal dosing was 45 hr. However, this may actually represent the half-life for absorption.

Distribution of radioactivity 48 hr after exposure:

Tissues

Dermal *

12.5 mg/kg bw

Urine

27.38 ± 3.06

Faeces

0.59 ± 0.41

Tissues & carcass

9.19 ± 0.93

14CO2

26.53 ± 2.73

Volatile organics

0.36 ± 0.45

Cage wash

0.70 ± 0.28

Dose site

32.80 ± 6.16

Total

97.54 ± 1.06

* Percent of dose

Values represent Mean ± SD for 4 animals.

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Objective of study:
toxicokinetics
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration and acclimation to the head-only chamber for approximately six days prior to the inhalation exposure

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h
Route of administration:
inhalation: vapour
Vehicle:
unchanged (no vehicle)
Details on exposure:
TYPE OF INHALATION EXPOSURE: nose only (dynamic flow-through conditions)

GENERATION OF TEST ATMOSPHERE / CHAMPER DESCRIPTION
The 14C-HEA vapour was generated by pumping air with an FMI pump (Fluid Metering Inc., Oyster Bay, NY) at the rate of 0.5 liters/min through a glass U-tube packed with glass beads and containing an aqueous solution of 1%-HEA. The 1%-HEA vapour exiting the U-tube was then diluted and mixed (in a J-tube packed with Teflon coated glass beads) with approximately 1.5 liters of air so that the total flow through the chamber was approximately 2.0 liters/min, and the target radioactivity of the vapour generated was approximately 0.2 µCi / liter. In order to accurately determine HEA exposure concentration, a sampling Port was positioned in the animals' breathing Zone to sample the chamber atmosphere. The HEA concentration and radioactivity were determined by sampling 103 mL/min of the chamber atmosphere onto silica gel tubes for 13.68 min. The 14C-HEA trapped on the silica gel was desorbed with a solution of 10% (10:90, v/v) acetonitrile in MILLI-Q @ water. Aliquots of these solutions were then analyzed by HPLC and liquid scintillation counting to determine the concentration of HEA and radioactivity in the chamber. Six samples of the chamber atmosphere were analyzed for HEA during the six hour exposure.

Duration and frequency of treatment / exposure:
once for a 6 hrs period
Dose / conc.:
8 ppm
Remarks:
corresponding to approx. 0.0385 mg/L
Recalculation based on the equation c(mg/m3) = molar mass (g) / molar volume (L) x c(mL/m3) with molecular weight (116.12 g/mol) and molar volume (24.1 L at 20 °C and 1013 hPa) [DFG, MAK List, Wiley-VCH Verlag, 2005].
No. of animals per sex per dose:
4
Control animals:
no
Details on study design:
After administration or termination of exposure to 14C-HEA, rats from all groups were housed in glass Roth-type metabolism cages. All urine, cage rinse, and feces were collected at specified intervals for up to 48 hr post-dosing or post-exposure and analyzed for radioactivity. In addition, expired organics and 14CO2 were trapped for the 48 hr post-dosing or post-exposure period. Urine and feces were also collected from individual rats during the inhalation exposure. During the inhalation exposure, the combined 14CO2 released into the inhalation chamber from the expired air of all 4 rats was trapped and analyzed after scrubbing 14C-HEA from the chamber exhaust. Selected samples of urine were analyzed by high performance liquid chromatography (HPLC) to determine 14C metabolic profiles.
The rats were sacrificed 48 hr after administration or exposure to 14C-HEA, and the radioactivity remaining in samples of blood, skin, and the carcass was quantified.
Radioactivity was quantified with a Beckman LS 3801 or Beckman LS 9000 liquid scintillation Counter (Beckman Instrument Inc., Fullerton, CA).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum, cage washes, bile, 14CO2
- Time and frequency of sampling:
urine (0-12, 12-24 and 24-48 hr post-dosing), faeces (at 24 hr intervals), 14CO2 (0.25, 0.5, 1, 2, 4, 8, and 12 hr post-exposure) (trapped in a mixture of CO2 trapping solution, monoethanolamine:methoxy-2-propanol, 3:7, v/v) and combustion scintillant (Spectrafluor@:methoxy-2-propanol:toluene 12:22:66, v/v)
During the inhalation exposure blood samples were collected at 0.25, 0.5, 1, 2, 4 and 6 hr, and 0.5, 1, 2, 4, 8, 20, 30 and 48 hr post inhalation exposure.
Statistics:
The half-lives for the CO2 excretion and the plasma radioactivity were determined from the slope of the line obtained by regression analysis of the excretion time-course obtained from each treatment group. Statistical analysis of the data was limited to the calculation of means and standard deviations where appropriate. Pharmacokinetic analysis (calculation of half-lives, AUC's etc.) were carried out using standard methodologies.
Details on distribution in tissues:
Following inhalation exposure, 39 % of activity recovered was eliminated in the urine and 41 % of the activity recovered was expired as 14CO2. The tissues and carcass accounted for 16 % of the activity recovered and 3 % of the recovered activity was in the faeces at 48 hr postdosing.
Details on excretion:
During the inhalation exposure an average of 25 % of the total radioactivity recovered from each animal was expired as 14CO2 by the end of the 6 hr exposure. As early as 1.5 hr post-exposure, approximately 3 % of the recovered radioactivity was excreted as 14CO2 in the breath. A total of 36 % of the recovered radioactivity was expired as 14CO2 during exposure and 12 hr post-exposure, indicating that the metabolism of inhaled 14C-HEA to 14CO2 occurred rapidly after absorption. The exhalation of 14CO2 derived from 14C-HEA appeared to follow first-order kinetics as a biphasic process, except following dermal administration.
During the 6 hr inhalation exposure 22 % of the recovered activity was excreted in the urine. By 12 hr post-exposure, 89 % of the total activity eliminated via this route had already been excreted.
Metabolites identified:
yes
Details on metabolites:
HPLC analyses were performed on pooled urine specimens from all treatment groups. Recovery from the HPLC System ranged from 90% to 114%. For all treatment groups, the radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

The test atmosphere averaged 8.9 ppm HEA with an activity of 0.215 µCi/liter air. The test atrnosphere ranged from 70 % to 138 % and 55 % to 112 % of the target HEA concentration and radioactivity concentrations, respectively. No signs of toxicity were observed following inhalation exposure.

During the inhalation exposure samples of urine and faeces were collected from individual animals. The combined 14CO2 expired by all four rats was also collected from the chamber exhaust. Therefore, the percent of the recovered dose received by inhalation exposure could be determined by calculating the µg equivalents of HEA recovered during and post-exposure. Based on µg equivalents of HEA, the inhalation dose was determined to be 12.7 mg/kg bw. Similarly, by comparing the areas under the plasma curves (AUC) for the oral and ip routes of administration to the plasma AUC for the inhalation route, the inhalation dose was determined to be equivalent to a 12 mg 14C-HEA/kg body weight.

The data show, that once systemically available, HEA is rapidly metabolized and eliminated from the body.

Half-lives:

Following the 8 ppm inhalation exposure, the half-life for the terminal phase of elimination via 14CO2 was determined to be approximately 19 hr. The half-life for the initial phase of elimination was 0.52.

For the inhalation exposure the half-life of elimination in the urine was determined to be 20 hr.

The half-life of elimination of radioactivity in the plasma was 24 hr for the 8 ppm inhalation treatment group.

Distribution of radioactivity 48 hr after exposure:

Tissues

Inhalation **

8 ppm

Urine

38.56 ± 7.05

Faeces

2.98 ± 1.12

Tissues & carcass

16.34 ± 1.76

14CO2

40.54

Volatile organics

0.84 ± 0.06

Cage wash

0.53 ± 0.28

Dose site

na

Total

100

**Percent of recovered radioactivity during the 6 hr exposure plus 14C-activity recovered in the 48 hr post-exposure.

Values represent Mean ± SD for 4 animals.

na: not applicable

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Objective of study:
toxicokinetics
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 / 12
Route of administration:
intraperitoneal
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The radiotracer was diluted with non-radiolabeled HEA to obtain a target radioactivity and concentration of 20 µCi and 1.75 and 36.7 mg/mL of dosing solution, respectively. Weighed aliquots of dosing solutions were analyzed for radioactivity using liquid scintillation counting.

VEHICLE
- distilled and deionised water
- Amount of vehicle (if gavage): 1.33 mL/kg of body weight
Duration and frequency of treatment / exposure:
once
Dose / conc.:
2.5 mg/kg bw/day
Dose / conc.:
50 mg/kg bw/day
No. of animals per sex per dose:
4
Control animals:
no
Details on study design:
After administration or termination of exposure to 14C-HEA, rats from all groups were housed in glass Roth-type metabolism cages. All urine, cage rinse, and feces were collected at specified intervals for up to 48 hr post-dosing or post-exposure and analyzed for radioactivity. In addition, expired organics and 14CO2 were trapped for the 48 hr post-dosing or post-exposure period. Selected samples of urine were analyzed by high performance liquid chromatography (HPLC) to determine 14C metabolic profiles.
The rats were sacrificed 48 hr after administration or exposure to 14C-HEA, and the radioactivity remaining in samples of blood, skin, and the carcass was quantified.
Radioactivity was quantified with a Beckman LS 3801 or Beckman LS 9000 liquid scintillation Counter (Beckman Instrument Inc., Fullerton, CA).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum, cage washes, bile, 14CO2
- Time and frequency of sampling:
urine (0-12, 12-24 and 24-48 hr post-dosing), faeces (at 24 hr intervals), 14CO2 (0.25, 0.5, 1, 2, 4, 8, and 12 hr post-exposure) (trapped in a mixture of CO2 trapping solution (monoethanolamine: methoxy-2-propanol, 3:7, v/v) and combustion scintillant (Spectrafluor@:methoxy-2-propanol:toluene 12:22:66, v/v)
Blood samples (100 µL) for the 14C plasma and red blood cell time-couse determinations were collected at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 30 and 48 hr after the administration of 14C-HEA by the ip route.
Statistics:
The half-lives for the CO2 excretion and the plasma radioactivity were determined from the slope of the line obtained by regression analysis of the excretion time-course obtained from each treatment group. Statistical analysis of the data was limited to the calculation of means and standard deviations where appropriate. Pharmacokinetic analysis (calculation of half-lives, AUC's etc.) were carried out using standard methodologies.
Details on distribution in tissues:
Following ip administration of 14C-HEA, between 91 and 95 % of the administered radioactivity was recovered in the urine, CO2, faeces, tissues and carcass, volatile organics and final cage wash.
Details on excretion:
At the low dose of 2.5 mg 14C-HEA/kg body weight, for the ip route of administration, approximately 43-47 % of the dose was eliminated in the urine, the primary elimination route, whereas 35-36 % of the dose was expired as 14CO2, and the tissues and carcass accounted for between 9-13 % of the dose. Less than 1.5 % of the administered dose of radioactivity was recovered in the faeces and less than 1 % was found in the final cage wash. Less than 0.2 % of the dose was recovered as volatile organics in the expired air.
At the higher dose of 50 mg/kg 14C-HEA/kg body weight, for the ip route of administration, 33-36 % of the dose was eliminated in the urine, whereas 40-45 % of the dose was expired as 14CO2. At this higher dose there was a shift from the urinary pathway as the primary route of elimination to the exhalation of 14CO2 as the primary route of elimination. As with the 2.5 mg/kg dose, the tissues and carcass accounted for 10-13 % of the dose and less than 0.6 % of the recovered radioactivity was in the final cage wash, less than 0.1 % was recovered as volatile organics in the expired air and less than 2.5 % of the dose was recovered in the faeces.
Following the ip route of administration, 0.3-1.5 % of the dose was expired as 14CO2 as early as 15 minutes post-dosing. The peak of CO2 excretion occurred during or before the 4-8 hr collection interval. By 12 hr post-dosing with 2.5 mg/kg for the ip route of administration, 31-32 % of the dose was expired as 14CO2. For this same collection interval following 50 mg/kg ip administration, 36 % of the dose was expired as 14CO2. The exhalation of 14CO2 derived from 14C-HEA appeared to follow first-order kinetics as a biphasic process, except following dermal administration.
Following ip administration, greater than 92 % of the total radioactivity excreted via the urine was excreted during the first 12 hr collection interval.
Metabolites identified:
yes
Details on metabolites:
HPLC analyses were performed on pooled urine specimens from all treatment groups. Recovery from the HPLC System ranged from 90% to 114%. For all treatment groups, the radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

The average 14C-HEA doses (mg/kg bw) administered to the ip treatment group ranged from 84 % to 107 % of target.

No signs of toxicity were observed following ip administration exposure.

The data show, that once systemically available, HEA is rapidly metabolized and eliminated from the body.

Half-lives:

Following the 2.5 mg/kg and the 50 mg/kg ip dose, the half-lives for the terminal phase of elimination via 14CO2 were determined to be approximately 18, and 17 hr, respectively. The half-lives for the initial phase of elimination were 2.6, and 1.8, respectively.

The half life of elimination of radioactivity in the urine following ip administration were 16 and 13 hr for the 2.5 mg/kg bw ip and 50 mg/kg bw ip treatment groups, respectively.

Following the the 2.5 and 50 mg/kg ip doses, peak plasma concentrations of 14C were seen at the first blood sample collected (15 min post-dosing). The plasma data collected past 30 min post-dosing indicated that the plasma radioactivity was eliminated in an apparent monophasic first-order manner. The half-lives of elimination of radioactivity in the plasma were 25, 29 hr for the following

treatment groups: 2.5 mg/kg ip, 50 mg/kg ip, respectively.

Distribution of radioactivity 48 hr after exposure:

Tissues

IP *

2.5 mg/kg bw

50 mg/kg bw

Urine

42.68 ± 4.26

35.85 ± 3.12

Faeces

0.76 ± 0.31

0.57 ± 0.14

Tissues & carcass

13.12 ± 1.64

13.16 ± 1.98

14CO2

34.87 ± 2.13

40.39 ± 3.88

Volatile organics

0.11 ± 0.07

0.09 ± 0.04

Cage wash

0.36 ± 0.13

0.58 ± 0.85

Dose site

na

na

Total

91.89 ± 6.43

90.64 ± 2.40

* Percent of dose

Values represent Mean ± SD for 4 animals.

na: not applicable

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Objective of study:
toxicokinetics
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h
Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The radiotracer was diluted with non-radiolabeled HEA to obtain a target radioactivity and concentration of 20 µCi and 1.75 and 36.7 mg/mL of dosing solution, respectively. Weighed aliquots of dosing solutions were analyzed for radioactivity using liquid scintillation counting.


VEHICLE
- distilled and deionised water
- Amount of vehicle (if gavage): 1.33 mL/kg of body weight
Duration and frequency of treatment / exposure:
once
Dose / conc.:
2.5 mg/kg bw/day
Dose / conc.:
50 mg/kg bw/day
No. of animals per sex per dose:
4
Control animals:
no
Details on study design:
After administration or termination of exposure to 14C-HEA, rats from all groups were housed in glass Roth-type metabolism cages. All urine, cage rinse, and feces were collected at specified intervals for up to 48 hr post-dosing or post-exposure and analyzed for radioactivity. In addition, expired organics and 14CO2 were trapped for the 48 hr post-dosing or post-exposure period. Selected samples of urine were analyzed by high performance liquid chromatography (HPLC) to determine 14C metabolic profiles.
The rats were sacrificed 48 hr after administration or exposure to 14C-HEA, and the radioactivity remaining in samples of blood, skin, and the carcass was quantified.
Radioactivity was quantified with a Beckman LS 3801 or Beckman LS 9000 liquid scintillation Counter (Beckman Instrument Inc., Fullerton, CA).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum, cage washes, bile, 14CO2
- Time and frequency of sampling:
urine (0-12, 12-24 and 24-48 hr post-dosing), faeces (at 24 hr intervals), 14CO2 (0.25, 0.5, 1, 2, 4, 8, and 12 hr post-exposure) (trapped in a mixture of CO2 trapping solution (monoethanolamine: methoxy-2-propanol, 3:7, v/v) and combustion scintillant (Spectrafluor@:methoxy-2-propanol:toluene 12:22:66, v/v)
Blood samples (100 µL) for the 14C plasma and red blood cell time-couse determinations were collected at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 30 and 48 hr after the administration of 14C-HEA by the oral route.


Statistics:
The half-lives for the CO2 excretion and the plasma radioactivity were determined from the slope of the line obtained by regression analysis of the excretion time-course obtained from each treatment group. Statistical analysis of the data was limited to the calculation of means and standard deviations where appropriate. Pharmacokinetic analysis (calculation of half-lives, AUC's etc.) were carried out using standard methodologies.
Details on distribution in tissues:
Following oral administration of 14C-HEA, between 91 and 95 % of the administered radioactivity was recovered in the urine, CO2, faeces, tissues and carcass, volatile organics and final cage wash.
Details on excretion:
At the low dose of 2.5 mg 14C-HEA/kg body weight, for the oral route of administration, approximately 43-47 % of the dose was eliminated in the urine, the primary elimination route, whereas 35-36 % of the dose was expired as 14CO2, and the tissues and carcass accounted for between 9-13 % of the dose. Less than 1.5 % of the administered dose of radioactivity was recovered in the faeces and less than 1 % was found in the final cage wash. Less than 0.2 % of the dose was recovered as volatile organics in the expired air.
At the higher dose of 50 mg/kg 14C-HEA/kg body weight, for the oral route of administration, 33-36 % of the dose was eliminated in the urine, whereas 40-45 % of the dose was expired as 14CO2. At this higher dose there was a shift from the urinary pathway as the primary route of elimination to the exhalation of 14CO2 as the primary route of elimination. As with the 2.5 mg/kg dose, the tissues and carcass accounted for 10-13 % of the dose and less than 0.6 % of the recovered radioactivity was in the final cage wash, less than 0.1 % was recovered as volatile organics in the expired air and less than 2.5 % of the dose was recovered in the faeces.
Following the oral route of administration, 0.3-1.5 % of the dose was expired as 14CO2 as early as 15 minutes post-dosing. The peak of CO2 excretion occurred during or before the 4-8 hr collection interval. By 12 hr post-dosing with 2.5 mg/kg for the oral route of administration, 31-32 % of the dose was expired as 14CO2. For this same collection interval following 50 mg/kg oral administration, 41 % of the dose was expired as 14CO2. The exhalation of 14CO2 derived from 14C-HEA appeared to follow first-order kinetics as a biphasic process, except following dermal administration.
Following oral administration, greater than 92 % of the total radioactivity excreted via the urine was excreted during the first 12 hr collection interval.
Metabolites identified:
yes
Details on metabolites:
HPLC analyses were performed on pooled urine specimens from all treatment groups. Recovery from the HPLC System ranged from 90% to 114%. For all treatment groups, the radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

The average 14C-HEA doses (mg/kg bw) administered to the oral treatment group ranged from 84 % to 107 % of target. No signs of toxicity were observed following oral administration exposure.

The data show, that once systemically available, HEA is rapidly metabolized and eliminated from the body.

Half-lives:

Following the 2.5 mg/kg and 50 mg/kg oral dose, the half-lives for the terminal phase of elimination via 14CO2 were determined to be approximately 15, and 14 hr, respectively. The half-lives for the initial phase of elimination were 1.9, and 1.8, respectively.

The half life of elimination of radioactivity in the urine following oral administration were 10, and 9 hr for the 2.5 mg/kg bw oral and 50 mg/kg bw oral treatment groups, respectively.

Following the 2.5 mg/kg oral dose, peak plasma concentrations of 14C were seen at the first blood sample collected (15 min post-dosing). However, following the 50 mg/kg oral dose, peak plasma concentrations were not found until 4 hr post-dosing. The plasma data collected past 30 min post-dosing indicated that the plasma radioactivity was eliminated in an apparent monophasic first-order manner. The half-lives of elimination of radioactivity in the plasma were 28, and 26 hr for the following treatment groups: 2.5 mg/kg oral, and 50 mg/kg oral, respectively.

Distribution of radioactivity 48 hr after exposure:

Tissues

Oral *

2.5 mg/kg bw

50 mg/kg bw

Urine

47.11 ± 1.62

33.07 ± 1.51

Faeces

1.33 ± 0.28

2.37 ± 1.26

Tissues & carcass

9.24 ± 1.18

10.19 ± 1.58

14CO2

36.00 ± 1.14

45.47 ± 0.66

Volatile organics

0.22 ± 0.21

0.10 ± 0.08

Cage wash

0.74 ± 0.54

0.39 ± 0.17

Dose site

na

na

Total

94.63 ± 1.39

91.59 ± 1.62

 

* Percent of dose

Values represent Mean ± SD for 4 animals.

na: not applicable

Endpoint:
basic toxicokinetics in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Objective of study:
metabolism
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 / 12
Details on study design:
Determination of In Vitro Half-life of 2-HEA in Blood:
To determine the in vitro rate of degradation or metabolism of 2-HEA in rat blood, male Fischer 344 rats were anesthetized with methoxyflurane and exsanguinated via cardiac puncture. The blood obtained was kept warm in a 37 °C temperature bath. 100-µL aliquots of blood were placed in vials in the water bath with the caps on loosely. Triplicate samples (along with corresponding blank) were prepared at three concentration levels (100, 10 and 1 µg 2-HEA/mL) for each time point selected. Solutions of 2-HEA for fortifying rat blood were prepared by diluting a measured volume of 2-HEA in 0.9 % saline solution to achieve a concentration of approximately 2000 µg/mL. This spiking solution was further diluted in saline for additional spiking solutions at approximate concentrations of 200 µg/mL and 20 µg/mL. Blood spikes were prepared by adding 5 µL of the appropriate spiking solution to the blood aliquots and then mixing using a vortex mixer. The blood spikes were then kept out of the bath and 500 µL of acetonitrile containing an internal standard (2-hydroxyethyl methacrylate, 2-HEMA at a concentration of 0.5 µg/mL) was added at 15 seconds, 30 seconds, 1 min, 2 min and 5 min after spiking. The vials were capped and the samples extracted for 2 minutes using a vortex mixer. The samples were centrifuged at 12500 g to remove proteinaceous materials prior to the analysis of the supernatant by gas chromatography-mass spectrometry. External standard solutions containing 2-HEA in the concentration range of 24.8 µg/mL to 0.0198 µg/mL and 2-HEMA at a constant concentration of 5 µg/mL were prepared in acetonitrile.
Quantification of 2-HEA in the blood extracts was based on comparison of the extract response to the external standard response taking into account the ratio of the 2-HEA response to that of the internal standard (2-HEMA). Using the ratio of the 2-HEA to 2-HEMA compensated for any volume or extraction differences which occurred during sample preparation.
Toxicokinetic parameters:
half-life 1st: The in vitro half-life of 2-HEA in rat blood at concentration of 1,10 or 1000 µg/mL was 103 ± 18 seconds or 1.7 min with no observed concentration dependence over two orders of magnitude.
Metabolites identified:
not measured

The in vitro half-life of 2-HEA in rat blood at concentration of 1,10 or 1000 µg/mL was 103 ± 18 seconds or 1.7 min with no observed concentration dependence over two orders of magnitude.

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

The metabolism, distribution and excretion of uniformly labelled 14C-2-hydroxyethyl acrylate was examined in male Fischer 344 rats using oral, intraperitoneal, dermal and inhalation routes of exposure (BAMM 1992). The results of the study indicate that once the chemical becomes systemically available, it is rapidly metabolized and eliminated from the body as either CO2 in the expired air or urinary metabolites. Greater than 70 % of the administered dose of HEA-derived 14C was excreted by 12 hr post-dosing or post-exposure as urinary metabolites and as 14CO2 in the expired air for the oral, ip, and inhalation routes.

No qualitative differences in urinary metabolites between routes were observed, indicating no marked route-dependent differences in the metabolic fate of HEA.

According to the metabolic scheme proposed by BAMM (1992) metabolism occurs by two primary routes, hydrolysis of the ester linkage by carboxylesterase to acrylic acid and ethylene glycol, and conjugation with glutathione (GSH). Both pathways serve to detoxify 2-hydroxyethyl acrylate. In rats, the metabolism of ethylene glycol proceeds via the alcohol and aldehyde dehydrogenase pathway finally resulting in the formation of CO2, and acrylic acid on the other hand is rapidly incorporated into the normal cellular metabolism via the propionate degradative pathway. Conjugation of 2-HEA with GSH can occur spontaneously by a Michael addition or can be mediated by GSH transferase. The conjugated form is rapidly excreted by the kidney.

 

Discussion on bioaccumulation potential result:

 

In vitro Studies

To determine the in vitro rate of degradation or metabolism of 2-HEA in rat blood, male Fischer 344 rats were anesthetized, exsanguinated via cardiac puncture and their blood obtained. Triplicate samples (along with corresponding blank) were prepared at three concentration levels (100, 10 and 1 µg 2-HEA/mL) for each time point selected. In addition to the 2-HEA spiking solutions, an internal standard (2-hydroxyethyl methacrylate, 2-HEMA, at a concentration of 0.5 µg/mL) was added at 15 seconds, 30 seconds, 1 min, 2 min and 5 min after spiking. Quantification of 2-HEA in the blood extracts by gas chromatography-mass spectrometry was based on comparison of the extract response to the external standard response taking into account the ratio of the 2-HEA response to that of the internal standard (2-HEMA).

 

The in vitro half-life of 2-hydroxyethyl acrylate in rat blood was approx. 100 sec (BAMM 1992).

 

In vivo Studies

The metabolism, distribution and excretion of uniformly labelled 14C-2-hydroxyethyl acrylate was examined in male Fischer 344 rats using oral, intraperitoneal, dermal and inhalation routes of exposure (BAMM 1992). For the oral and intraperitoneal routes of exposure rats (4 animals/dose level/route of exposure) received a single dose of 2.5 or 50 mg/kg body weight (approximately 20μCi), respectively. For the inhalation exposure six rats were exposed to a target vapor concentration of 8 ppm (corresponding to approx. 0.0385 mg/L and to approx. 0.2 µCi/L) 14C-HEA for 6 hours nose only under dynamic flow-through conditions. For the dermal exposure 4 rats were treated under occlusive conditions with 14C-HEA at a dose of 12.5 mg/kg body weight (approximately 15-20μCi).

The results of the study indicate that once the chemical becomes systemically available it is rapidly metabolized and eliminated from the body as either CO2 in the expired air or urinary metabolites. Greater than 70 % of the administered dose of HEA-derived 14C was excreted by 12 hr post-dosing or post-exposure as urinary metabolites and as 14CO2 in the expired air for the oral, ip, and inhalation routes.

For the oral and intraperitoneal routes (2.5 mg/kg bw) 35-36 % of the administered dose was expired as 14CO2 and 43 - 47 % of the dose excreted via urine by 48 hours post-dosing. At 50 mg/kg bw following oral and ip administration, there was some evidence of saturation kinetics, with 40 – 45 % of the dose expired as 14CO2 and 33 – 36 % of the dose excreted in the urine. The rate of absorption of HEA appeared to be route-dependent and was complete within 4 hr or less when HEA was given by the oral or ip routes of administration.

Following dermal administration 66 % of the dose was slowly absorbed within 48 hours of the application with the remaining 33 % being associated with the application site. Of the absorbed dose, 27 % was excreted in the urine as metabolites of HEA and 27 % was excreted in the expired air as 14CO2.

For inhalation, 39 % of the 14C-activity recovered at 48 hr was eliminated in the urine and 41 % was expired as 14CO2.

For all routes, 9 – 16 % of the dose or recovered activity was found in the tissues and carcass and less than 3 % in the faeces.

The half-lives of elimination of radioactivity in the urine and for expired 14CO2 were 14 h and 17 h, respectively. The half-life of elimination of radioactivity in the plasma was determined to be 26 hr and did not represent parent chemical.

No qualitative differences in urinary metabolites between routes were observed, indicating no marked route-dependent differences in the metabolic fate of HEA. HPLC analyses were performed on pooled urine specimens from all treatment groups and exposure routes. Radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

The available metabolic data on HEA is consistent with information on other acrylates where hydrolysis of the ester functionality is the primary metabolic pathway. By analogy with e.g. ethyl acrylate or acrylic acid it is expected that a minor metabolic pathway for HEA will be via conjugation with glutathione with the resulting mercapturic acid derivatives being excreted in the urine. This is supported by the identity of one of the major urinary metabolites of HEA.

 

Conclusion

 

Animal studies indicated rapid metabolism via hydrolysis of the ester functionality with the subsequent rapid metabolism of the hydrolysis products to produce exhaled CO2 or urinary metabolites (mercapturic acid derivatives). There were no marked route-dependent differences in the metabolic fate of HEA when administered by the oral, intraperitoneal, dermal or inhalation routes of exposure.

 

Discussion on absorption rate:

The metabolism, distribution and excretion of uniformly labelled 14C-2-hydroxyethyl acrylate was examined in male Fischer 344 rats using dermal application (BAMM 1992). 4 rats were treated under occlusive conditions with 14C-HEA at a dose of 12.5 mg/kg body weight (approximately 15-20μCi).

Following dermal administration, 66 % of the dose was slowly absorbed within 48 hours of the application with the remaining 33 % being associated with the application site. Of the absorbed dose 27 % was excreted in the urine as metabolites of HEA and 27 % was excreted in the expired air as 14CO2. HPLC analyses were performed on pooled urine specimens. Radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS.

The dermal absorption of HEA was relatively slow with a half-life in the order of 24 hr or greater, which was confirmed by plasma and red blood cell radioactivity concentration-time curves, amount remaining on the skin at sacrifice, and the lag time in peak urinary and CO2 excretion.