Methyl 4-hydroxybenzoate

Toxicity to reproduction: other studies

Administrative data

Endpoint:

toxicity to reproduction: other studies

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

received: 5. May 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well performed guideline-conform study with restricted reporting.

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: OECD 440

Deviations:

yes

Remarks:

analysis of phytoestrogens in diet and daily body weight not reported, 5 animals/dose group

Principles of method if other than guideline:

n.a.

GLP compliance:

not specified

Type of method:

in vivo

Test material

Test material information

Constituent 1

Reference substance name:

Methyl 4-hydroxybenzoate

EC Number:

202-785-7

EC Name:

Methyl 4-hydroxybenzoate

Cas Number:

99-76-3

Molecular formula:

C8H8O3

IUPAC Name:

methyl 4-hydroxybenzoate

Constituent 2

Reference substance name:

Methylparaben

IUPAC Name:

Methylparaben

Details on test material:

Supplier: Aldrich Chemical Company (Gilligham, Dorset, UK)
Puritiy: > 99%

Test animals

Species:

rat

Strain:

other: Alpk:AP

Sex:

female

Details on test animals or test system and environmental conditions:

Immature rats: 21-22 days old, 35-38 g; from Zeneca breeding unit (Alderley Park)
Ovariectomised rats: obtained from Zeneca breeding unit (Alderley Park). The ovariectomy was performed on 6 to 8 week old animals.They were maintained for 2 weeks after the operation, during which time daily vaginal smears were taken, and only noncycling animals were used for the uterotrophic assay.

Husbandry:
All animals were housed in wire mesh cages; solid bottoms were provided for immature animals. Temperature was controlled at 22+/-3°C, humidity was controlled at 30-70%, and a 12 h/12 h light dark cycle was maintained. Animals were weaned on R&M No. 3 (Special Diet Services Ltd., William Essex, UK) at postnatal Days 19-21 and maintained on R&M No. 1 (Special Diet Services Ltd.) from postnatal Day 21 omward. Diet and water were available ad libitum.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

arachis oil

Details on exposure:

Each experiment was accompanied by a vehicle control group (arachis oil) and a positive control group (17ß-Estradiol (0.4 mg/kg bw/d) by oral gavage or subcutaneous injection. Animals were dosed on 3 successive days with Methylparaben/17ß-Estradiol dissolved/suspended in Arachis oil. The maximum doses used were determined by turbidity of the dosing solutions and restriction of dosing volume.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no data

Duration of treatment / exposure:

3 days

Frequency of treatment:

Daily

Duration of test:

Ovariectomised rats:
- Ovariectomy on 6-8 week old rats
- 2 weeks maintainance after operation (only noncycling females were used for assay)
- 3 days treatment, necropsy 24 h after last treatment

Immature rats:
- 24 h acclimatisation
- 3 days treatment, necropsy 24 h after last treatment

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
40 mg/kg bw/d
Basis:
actual ingested

Doses / concentrations 2

Remarks:

Doses / Concentrations:
400 mg/kg bw/d
Basis:
actual ingested

Doses / concentrations 3

Remarks:

Doses / Concentrations:
800 mg/kg bw/d
Basis:
actual ingested

Doses / concentrations 4

Remarks:

Doses / Concentrations:
40 mg/kg bw/d
Basis:
other: subcutaneous

Doses / concentrations 5

Remarks:

Doses / Concentrations:
80 mg/kg bw/d
Basis:
other: subcutaneous

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

Negative control: Arachis oil
Positive control: 17ß-Estradiol
Animals were killed by an overdose of halothane 24 h after the final dose. Vaginal opening was recorded for immature animals at the time of death. Vaginal smears were also taken from ovariectomised animals at the time of death. Uteri were excised, trimmed free of fat, pierced, and blotted to remove excess fluid. The body of the uterus was cut just above its junction with the cervix and at the junction of the uterine horns with the ovaries. The uterus was then weighed (wet weight). Uterine dry weight was also determined by drying the uteri at 70°C for 24 h before reweighing. A quantitative estimation of vaginal cytology was performed by counting the number of fully cornified cells in at least 2 fields containing a total of at least 100 cells (x200 magnification).

Statistics:

Variation within experiments for uterus wet and dry weights was determined by analysis of variance using the GLM procedure. Percentages of cornified cells were also considered by analysis of variance, following a double arcsine transformation (Freeman and Turkey, 1950). Differences from control values were assessd statistically using a two-sided Student´s t test based on the error mean square from the analysis of variance.

Results and discussion

Effect levels

Dose descriptor:

NOEL

Effect level:

800 mg/kg bw/day (actual dose received)

Sex:

female

Basis for effect level:

other: no increase in uterus weights or premature vaginal opening

Observed effects

No clinical signs
No increases in uterus weight
No premature vaginal opening
No increase in vaginal cornification

Any other information on results incl. tables

Table 1: The Activity of Methylparaben in the Immature Rat Uterotrophic Assay

 

Compound	Dose/	Route	Uterus weight/[mg]
	[mg/kg bw/d]		Wet	Dry
Estradiol	0.4	oral	117.5±8.9^*	22.5±1.8^*
Arachis oil	10 mL/kg bw/d	oral	33.8±5.9	6.4±0.9
Methylparaben	40	oral	34.5±3.2	6.8±0.7
Methylparaben	400	oral	33.3±5.3	6.3±0.9
Methylparaben	800	oral	31.0±4.3	6.2±0.7
Methylparaben	40	subcutaneous	33.5±6.6	6.8±1.1
Methylparaben	80	subcutaneous	32.8±1.5	6.6±0.3

^*    p<0.01

Applicant's summary and conclusion

Conclusions:

Methylparaben (orally as well as subcutaneously applied to immature/ovariectomised rats) was inactive in this uterotrophic assay at concentration up to 800 mg/kg bw/d (NOEL).

Executive summary:

Methylparaben was administered to immature and ovariectomised rats assigned to 5 groups of 5 animals each at doses of 40, 400, 800 mg/kg bw/d (orally) and 40, 80 mg/kg bw/d (subcutaneously). 24 h after the last (third) administration, the rats were sacrificed, the weight of the uteri (wet and dry) was recorded and a quantitative estimation of the vaginal cytology was performed. There were no effects in any group. Based on the results of this assay the respective NOEL is > 800 mg/kg bw/d.