2-butoxyethanol

Endocrine disrupter testing in aquatic vertebrates – in vivo

Administrative data

Endpoint:

amphibian: other

Remarks:

Inhibition of germinal vesicle breakdown in vitro

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:

Inhibition of germinal vesicle breakdown in Xenopus oocytes in vitro by a series of substituted glycol ethers

Author:

Fort DJ, Mathis MB, Guiney PD, Weeks JA.

Year:

2017

Bibliographic source:

J Appl Toxicol. 2017;1–10.

Materials and methods

Principles of method if other than guideline:

- Principle of test: A 24 hour in vitro Xenopus oocyte maturation (germinal vesicle breakdown [GVBD]) assay
- Parameters analysed / observed: progesterone or androstenedione binding affinities to the oocyte plasma membrane progesterone receptor (OMPR) or classical androgen receptor
- This assay is only used by a few labs and is not well established. It also doesn’t appear to have gone through a rigorous validation.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

2-butoxyethanol

EC Number:

203-905-0

EC Name:

2-butoxyethanol

Cas Number:

111-76-2

Molecular formula:

C6H14O2

IUPAC Name:

2-butoxyethanol

Specific details on test material used for the study:

Source: Sigma Aldrich
Purity: 99.4%

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

yes

Remarks:

Oocyte Ringer's buffer (pH 7.8)

Test organisms

Aquatic vertebrate type:

frog

Test organisms (species):

Xenopus laevis

Details on test organisms:

TEST ORGANISM
- Source: Dexter, MI
- Life stage: adult

ACCLIMATION
- Acclimation period: 120 days

METHOD FOR PREPARATION AND COLLECTION OF EGGS
- Animals were killed in 0.2% (w/v) 3‐aminobenzoic acid ethyl ester immediately before ovary excision

Study design

Test type:

other: in vitro

Test conditions

Nominal and measured concentrations:

0.001, 0.01, 0.05, 0.1, 0.5, 1.0, 5.0 and 10.0 mg/L. Tested in triplicate with and without the presence of 250 μM progesterone or 250 μM androstenedione:

Details on test conditions:

TEST SYSTEM
- Test vessel: six‐well glass culture plates,
- No. of organisms per vessel: 20 oocytes per replicate
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- Vehicle control performed: yes
- No. of vessels per vehicle control (replicates): 3

Reference substance (positive control):

not required

Remarks:

Mutliple substances studied. 2-methoxyethanol used as reference substance

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

24 h

Dose descriptor:

other: IC25

Effect conc.:

1.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: progesterone induced GVBD inhibition

Remarks on result:

other: 0.5% of the potency of 2-methoxyethanol. 95% CI 1150 - 1650). Equiv to 1.2E-05M

Effect concentrations 2

Duration:

24 h

Dose descriptor:

other: IC25

Basis for effect:

other: Androstenedione‐induced GVBD inhibition potencies

Remarks on result:

not determinable

Remarks:

not reached at maximum tested concentration of 10mg/L (8.5e-05M)

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Executive summary:

A 24 hour in vitro Xenopus oocyte maturation (germinal vesicle breakdown [GVBD]) assay was used to screen 2-butoxyethanol for possible endocrine disruption.  ). It inhibited progesterone but not androstenedione induced GVBD although the effect was very weak (IC25 200x lower than that for 2-methoxyethanol.  The assay seems to be very sensitive (prone to false positives) compared to mammalian systems and does not provide any substantive evidence of a possible endocrine mode of action.