Tetramethylene dimethacrylate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline available

Principles of method if other than guideline:

Determination of in vitro hydrolysis rates of methacrylate esters; determination of half-lifes in rat liver microsomes and whole rat blood. determination of Km and Vmax values for ester hydrolysis in rat liver microsomes; these values were used for PBPK modeling to simulate in vivo blood concentrations

GLP compliance:

yes

Specific details on test material used for the study:

- Name of test material (as cited in study report): 1,4-Butanediol dimethacrylate

Radiolabelling:

no

Species:

other: rat liver microsomes and rat blood

Vehicle:

DMSO

Duration and frequency of treatment / exposure:

phase I: 120 min (samples collected at 0, 2, 5, 15, 30, 60 and 120 minutes)
phase II: 5 min (samples collected at 0 and 5 minutes)

Dose / conc.:

0.25 other: mM

Remarks:

phase I

Dose / conc.:

0.05 other: mM

Remarks:

phase II

Dose / conc.:

0.1 other: mM

Remarks:

phase II

Dose / conc.:

5 other: mM

Remarks:

phase II

No. of animals per sex per dose / concentration:

not applicable; in vitro test

Control animals:

other: not applicable; in vitro test

Positive control reference chemical:

Methyl methacrylate

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Method type(s) for identification: liquid chromatography separation with accurate mass quadrupole/time-of-flight mass spectrometry detection (LC/QTOF-MS) to quantitate methacrylic acid concentrations
- Limits of detection and quantification: LLQ (phase I) = 0.0117 mM methacrylic acid; LLQ (phase II) = 0.00509 mM methacrylic acid

Type:

metabolism

Results:

the ester was rapidly converted to MAA in whole rat blood (Phase I) and rat liver microsomes (Pase II): half life 4.46 min (liver microsomes) / 4.10 min (blood). In phase II hydrolyses exp. 2 mol of MAA was produced for every mol 1,4-BDDMA

Negative controls in the rat liver microsome experiments included incubations with heat-inactivated microsomes, no microsomes and no NADPH. Removal of NADPH made little or no difference in hydrolysis rates. Heat inactivation significantly reduced hydrolysis rates, and absence of microsomes resulted in no hydrolysis. 

1,4 -BDDMA was rapidly converted to MAA in whole rat blood and rat liver microsomes with hydrolysis half-lives of 4.46 min (liver microsomes) and 4.10 min (blood).

Vmax (in vitro) = 129 nmol/min/mg

Vmax (in vivo) = 160 mg/hr/g liver

Km (in vitro) = 83 µM

Km (in vivo) = 19 mg/L

PBPK modelling showed rapid hydrolysis of 1,4 -BDDMA.

Conclusions:

Interpretation of results (migrated information): other: The metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.
The metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.

Executive summary:

This in vitro metabolism study was conducted to investigate in vitro hydrolysis rates of 1,4 -BDDMA. Half-lifes were determined in rat liver microsomes and whole rat blood. Further experiments were conducted to determine Km and Vmax values for ester hydrolysis in rat liver microsomes. These values were used for PBPK modelling.

1,4 -BDDMA was rapidly converted to MAA in whole rat blood and rat liver microsomes with hydrolysis half-lives of 4.46 min (liver microsomes) and 4.10 min (blood).

Vmax (in vitro) = 129 nmol/min/mg

Vmax (in vivo) = 160 mg/hr/g liver

Km (in vitro) = 83 µM

Km (in vivo) = 19 mg/L

In summary, the metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.

Reference 2

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Reason / purpose for cross-reference:

other: same study protocol

Qualifier:

no guideline available

Principles of method if other than guideline:

Determination of in vitro hydrolysis rates of methacrylate esters; determination of half-lifes in rat liver microsomes and whole rat blood. determination of Km and Vmax values for ester hydrolysis in rat liver microsomes.

GLP compliance:

yes

Specific details on test material used for the study:

Lot #: 2026062020
Purity 92.25%

Radiolabelling:

no

Species:

other: rat liver microsomes and rat blood

Strain:

Fischer 344

Vehicle:

DMSO

Duration and frequency of treatment / exposure:

120 min (samples collected at 0, 2, 5, 15, 30, 60 and 120 minutes)

Dose / conc.:

0.25 other: mM

Remarks:

Whole blood

Dose / conc.:

0.229 other: mM

Remarks:

Liver Microsomes

No. of animals per sex per dose / concentration:

not applicable; in vitro test

Control animals:

other: not applicable; in vitro test

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Method type(s) for identification: liquid chromatography separation with accurate mass quadrupole/time-of-flight mass spectrometry detection (LC/ESI/QTOF-MS) to quantitate methacrylic acid concentrations

Statistics:

Descriptive statistics were used, i.e., mean ± standard deviation. All calculations in the database were conducted using Microsoft Excel (Microsoft Corporation, Redmond, Washington) spreadsheets and database was set to full precision mode (15 digits of accuracy).

Type:

metabolism

Results:

The ester was rapidly converted to MAA in whole rat blood (5.63 min) and rat liver microsomes (3.48 min).

Metabolites identified:

yes

Details on metabolites:

Methacrylic acid

1,4 -BDDMA was rapidly converted to MAA in whole rat blood and rat liver microsomes with hydrolysis half-lives of 3.48 min (liver microsomes) and 5.63 min (blood).

Based on the half-live values, the intrinsic clearance rate Cl_intand elimination rate k_evalues for 1,4-BDDMA in rat liver microsomal incubation conditions, were calculated as 119µl/min/mg and 0.199 min^-1, respectively.

Based on the half-live values, the intrinsic clearance rate Cl_intand elimination rate k_evalues for 1,4-BDDMA in rat whole blood incubation conditions, were calculated as 246 µl/min/mg and 0.123 min^-1, respectively.

Conclusions:

Interpretation of results (migrated information): other: The metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.
The metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.

Executive summary:

This in vitro metabolism study was conducted to investigate in vitro hydrolysis rates of 1,4 -BDDMA. Half-lifes were determined in rat liver microsomes and whole rat blood. Further experiments were conducted to determine Km and Vmax values for ester hydrolysis in rat liver microsomes. These values were used for PBPK modelling.

1,4 -BDDMA was rapidly converted to MAA in whole rat blood and rat liver microsomes with hydrolysis half-lives of 4.46 min (liver microsomes) and 4.10 min (blood).

Vmax (in vitro) = 129 nmol/min/mg

Vmax (in vivo) = 160 mg/hr/g liver

Km (in vitro) = 83 µM

Km (in vivo) = 19 mg/L

In summary, the metabolism data and modelling results show that 1,4-BDDMA would be rapidly hydrolysed in the rat.

Reference 3

Endpoint:

dermal absorption

Type of information:

(Q)SAR

Remarks:

Based on an established human skin model by Potts and Guy (Potts RO and Guy RH (1992). Predicting Skin Permeability. Pharm. Res. 9(5): 663-669)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Principles of method if other than guideline:

The physicochemical parameters of MW, Log P and saturated aqueous solubility have been used in the evaluation of 56 methacrylate compounds. An output of predicted steady-state flux was calculated using the principles defined in the Potts and Guy prediction model. (Potts RO and Guy RH (1992). Predicting Skin Permeability. Pharm. Res. 9(5): 663- 669)

GLP compliance:

no

Specific details on test material used for the study:

- Name of test material (as cited in study report): 1,4-Butandiol dimethacrylate

Species:

other: human skin model

Details on test animals or test system and environmental conditions:

not applicable; in silico modelling

Type of coverage:

other: not applicable; in silico modelling

No. of animals per group:

not applicable; in silico modelling

Absorption in different matrices:

predicted flux 2.895 μg/cm²/h; the relative dermal absorption is low

Based on a molecular weight of 226.27 g/mol and a g Kow of 3.1, the predicted flux of 1,4 -BDDMA is 2.895 μg/cm²/h; the relative dermal absorption is low.

Conclusions:

The dermal absorption of 1,4-BDDMA is predicted to be low; the predicted flux is 2.895 μg/cm²/h.

Executive summary:

The dermal absorption (steady-state flux) of 1,4 -BDDMA has been estimated by calculation using the principles defined in the Potts and Guy prediction model.

Based on a molecular weight of 226.27 g/mol and ag Kow of 3.1, the predicted flux of 1,4 -BDDMA is 2.895 μg/cm²/h; the relative dermal absorption is low.

Description of key information

Absorption
Based on the physico-chemical properties (molecular weight, physical state, water solubility, lipophilicity) of tetramethylene dimethacrylate, the substance favours absorption from the gastrointestinal tract after oral administration.

Due to the low vapour pressure of 0.1 Pa at 20°C (below the general cut-off value of 0.5 kPa (ECHA, 2017)), inhalation of the substance as vapour is very unlikely since the volatility is too low. Solid particles, however, could be absorbed after inhalation of an aerosolized substance, although this does not seem likely considering the size of the molecule.

Tetramethylene dimethacrylate has a relatively low ability to be absorbed through the skin due to its molecular weight of 226.27 g/mol. The ability of partitioning from the stratum corneum into the epidermis is moderate due to the water solubility of 243 mg/l. Additionally, the log P_OW favours the penetration into the stratum corneum and hence the absorption across the skin. The predicted steady-state flux was determined at 2.895 μg/cm²/h and is low in comparison to other methacrylates. It is known that the ester bonds of tetramethylene dimethacrylate is hydrolysed in the skin by carboxyl esterases, although to a much lesser extent than in the gastrointestinal tract due to the lower level of enzymes.

"In the absence of more specific data, absorption can be assumed to occur via oral and dermal routes. Tetramethylene dimethacrylate is unlikely to be absorbed via inhalation." (cited from the CLH report of the Finnish CA).

Distribution
Tetramethylene dimethacrylate undergoes enzymatic hydrolysis especially in the gastrointestinal tract, the breakdown products (methacrylic acid and alcohol moiety) are likely to be widely distributed due to their small size and solubility in aqueous media. Due to the logP_OW of 3.10, the parent compound has a high permeability across lipid membranes. In contrast to the metabolites which contains no lipohilic groups and the likelihood to cross membranes is considered to be low. Furthermore, the available data do not show accumulation in any organ or tissue, either. No target organs have been identified for tetramethylene dimethacrylate.

Metabolism
In the first step, one of two the ester bonds of tetramethylene dimethacrylate is hydrolysed by carboxyl esterases to produce the corresponding mono-ester. Then, the second ester bond is hydrolysed by the same group of enzymes to produce methacrylic acid (MAA) and the corresponding alcohol, 1,4-butanediol.

The half-live of the conversion of tetramethylene dimethacrylate to methacrylic acid was determined to be 4.46 minutes in rat liver microsomes and 4.10 minutes in whole rat blood (Dow, 2013). In a second determination, the half-live was determined to be 3.48 minutes in rat liver microsomes and 5.63 minutes in whole rat blood (Dow, 2017).

In general, the metabolism rates for alkyl-methacrylates are approximately 20 times lower in skin microsomes than in liver microsomes.

The primary methacrylic metabolite, methacrylic acid, will predominantly be metabolised in the liver through the valine pathway and the citric acid cycle (Rawn, 1983; Shimomura et al., 1994; Boehringer, 1992) and be exhaled as CO₂.

The alcohol, 1,4-butanediol is rapidly transformed to gamma-hydroxybutyric acid and subsequently to succinic semialdehyde (NTP, 1996). The aldehyde is then converted to succinic acid, which is degraded via the citric acid cycle and exhaled as CO₂.

A QSAR model for 1,4-BDDMA predicted only slight reactivity with glutathione for the ester and no reactivity for the primary metabolite, methacrylic acid (Cronin, 2012).  Studies with methacrylates in vitro confirm their low reactivity with GSH, in particular compared to the corresponding acrylates, and have proposed that this is due to steric hindrance of the addition of a nucleophile at the double bond by the alpha-methyl side-group (McCarthy & Witz, 1991, McCarthy et al., 1994, Tanii and Hashimoto, 1982). Consequently, glutathione conjugation only plays a minor role in the metabolism of alkyl and multifunctional methacrylate esters (e.g. tetramethylene dimethacrylate).

Excretion
Due to the rapid hydrolysis of Tetramethylene dimethacrylate, the substance is unlikely to be excreted as such.  The metabolites of the substance (Methacrylic acid and 1,4-butanediol) will be cleared from blood circulation by physiological pathways, and most of the received dose will be exhaled as CO₂.

 

 

 

 

 

 

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

100

Absorption rate - inhalation (%):

100

Additional information

Conclusion

Summary and discussion on toxicokinetics

Methacrylate esters are absorbed mainly orally and in minor extent dermally. Tetramethylene dimethacrylate is rapidly hydrolysed by carboxylesterases to methacrylic acid (MAA) and 1,4-butanediol. Ester hydrolysis can occur in local tissues at the site of contact as well as in blood and other organs by non-specific carboxylesterases. By far the highest enzyme activity has been shown in liver microsomes indicating that the parent ester will be fully metabolised in the liver. Clearance of the parent ester from the body is in the order of minutes. The primary methacrylic metabolite, MAA, is subsequently cleared rapidly from blood by standard physiological pathways, with most of the administered dose being exhaled as CO2. 1,4-Butanediol will be transformed rapidly by alcohol dehydrogenases and aldehyde dehydrogenases into γ-hydroxybutyric acid and will be converted to succinic acid by γ -hydroxybutyric acid dehydrogenase. Methacrylic acid, γ-hydroxybutyric acid and succinic acid will be degraded through the tricarboxylic acid cycle and primarily excreted as CO2.

 

Compliance to REACh requirements

The information requirement is covered with reliable in vitro studies on the primary metabolism, reliable in vitro/ in vivo studies on the metabolism of the methacrylic metabolite MAA as well as reliable publication data on the metabolism of the alcohol metabolite 1,4-BD. All mentioned sources are reliable (Reliability 1 or 2) so that the category/ read across approach can be done with a high level of confidence.