3-hydroxy-2-methyl-4-pyrone

Toxicity to reproduction

Administrative data

Endpoint:

fertility, other

Remarks:

One Generation Reproductive Toxicity/Combined Chronic Toxicity & Carcinogenicity Study

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

The study was performed before the introduction of OECD guidelines but is, however, considered valid by the EFSA.

Data source

Reference

Reference Type:

publication

Title:

Toxicity studies with Ethyl Maltol

Author:

Gralla, E.J., Stebbins, R.B., Coleman, L., Delahunt, C.S.,

Year:

1969

Bibliographic source:

Toxicology and applied pharmacology, 15, 604-613

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The study was performed before the introduction of OECD guidelines but is, however, considered valid by the EFSA. It was similar to a One Generation Reproductive Toxicity (OECD 415) and Combined Chronic Toxicity & Carcinogenicity Study (OECD 453). Groups of 25 male and 25 female Charles River rats received ethyl maltol in the diet at dose levels of 50, 100 or 50 mg/k bw/day for 2 years. Blood and urine examinations were made after 3, 6, 9, 12, 18 and 24 months. Between 15 and 21 and 30 and 36 weeks, 10 males and 10 females per level were mated to produce two separate litters. The resulting offspring were counted, weighed, and examined for abnormal development at birth and during lactation. At weaning they were sacrificed and examined for internal malformations. In the parent groups, 5 of each sex at each level were autopsied after 1 year on test, the remainder after 2 years. Gross and microscopic evaluations were carried out.

EFSA Journal 2015;13(9):4244

GLP compliance:

no

Limit test:

no

Justification for study design:

The study (One Generation Reproductive Toxicity/Combined Chronic Toxicity & Carcinogenicity Study) was performed before the introduction of OECD guidelines but is, however, considered valid by the EFSA.

Test material

Test material information

1

Reference substance name:

2-ethyl-3-hydroxy-4-pyrone

EC Number:

225-582-5

EC Name:

2-ethyl-3-hydroxy-4-pyrone

Cas Number:

4940-11-8

Molecular formula:

C7H8O3

IUPAC Name:

2-ethyl-3-hydroxy-4H-pyran-4-one

Test material form:

solid

Test animals

Species:

rat

Strain:

other: Charles River albino

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River
- Age at study initiation: Weanling
- Housing: Individually caged
- Diet: Rockland Ground Rat Food ad libitum
- Water: ad libitum

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
Rockland Ground Rat Food was mixed with ethyl maltol

Details on mating procedure:

Between 15 and 21 and 30 and 36 weeks, 10 males and 10 females per level were mated to produce two separate litters.

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

2 years

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

200 mg/kg bw/day (nominal)

No. of animals per sex per dose:

25 males and 25 females

Control animals:

yes, plain diet

Examinations

Parental animals: Observations and examinations:

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights consumption were measured weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
Food consumption were measured weekly and test item concentrations in food were adjusted accordingly.

HAEMATOLOGY: Yes; Blood examinations were made after 3, 6, 9, 12, 18 and 24 months (hemoglobin, hematocrit, RBC, total WBC, and differential count).

CLINICAL CHEMISTRY: Yes; At the completion of this study, all rats were anesthetized and bled from the abdominal aorta using heparinized syringes. Samples were centrifuged and plasma glucose values determined.

URINALYSIS: Yes; Urine examinations were made after 3, 6, 9, 12, 18 and 24 months (color, volume, specific gravity, pH, blood, albumin, glucose, and microscopic examination of the sediment after centrifugation)..

Litter observations:

Offspring were counted, weighed, and examined for abnormal development at birth and during lactation.

Postmortem examinations (parental animals):

GROSS PATHOLOGY: Yes ; In the parent groups, 5 of each sex at each level were autopsied after 1 year on test, the remainder after 2 years. The following organs were removed, trimmed, and weighed: heart, lung, liver, kidney, pancreas, spleen, thymus, mesenteric lymph node, adrenals, thyroid, brain, hypophysis, uterus and ovary; these, plus additional tissues, were placed in Bouins’ solution, except the eyes and nervous system tissue which were fixed in 15 % formalin.

HISTOPATHOLOGY: Yes; All specimens were embedded in paraffin, sectioned, and stained with hematoxylin and eosin. The following tissues of 5 rats of each sex at each level were examined microscopically: brain (sectioned at the optic chiasm, mammillary body, cerebellum, pons, and medulla oblongata), cervical spinal cord, hypophysis, eye, parotid gland, thyroid and parathyroid, thymus, heart, lung, sternum, rib, aorta, liver, spleen, pancreas, kidneys, adrenals, stomach (fore and hind), small and large intestine (four levels), mesenteric lymph node, reproductive tract (all levels), urinary bladder, skeletal muscle, femoral nerve, femoral bone marrow, skin and mammary gland

Postmortem examinations (offspring):

At weaning, offspring were sacrificed and examined for internal malformations.

Reproductive indices:

Percent conception, Average litter size at birth,

Offspring viability indices:

Pup survival at Day 21, average litter size 21 days and average weight, pups at 21 days lactation were recorded.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Description (incidence):

All dose levels of ethyl maltol were well tolerated throughout the 2-year feeding period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

The test and control animals grew and maintained the body weight in a comparable manner.

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

After two years on test, one control rat had a massive anemia (RBC, 1.8 x 10*3/mm3; hemoglobin, 8.0g% and hematocrit, 18.5 %) of unknown etiology. Otherwise, all hematologic values for test and control animals were within normal ranges.

Clinical biochemistry findings:

not examined

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

All rats showed a tendency toward albuminuria; otherwise, urinalysis values were essentially normal.

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Pathologic changes consistent with aged rats were observed primarily in the pulmonary, endocrine, urinary, and cardiovascular systems (Table 5).

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Neoplasia occurred in a random manner with no apparent relationship between number, location, or type of tumors and treatment (Table 6).

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, non-treatment-related

Description (incidence and severity):

A fall in fertility was noted in test and control groups at the second mating but controls were affected also (60% conception at 200 mg/kg bw/day Ethyl maltol, 50% controls; Table 3). This was due presumably to the advanced age of the animals.

Ethyl maltol had no effect on gestation, parturition or lactation.

Effect levels (P0)

Dose descriptor:

NOAEL

Effect level:

>= 200 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: Highest dose tested

Target system / organ toxicity (P0)

Critical effects observed:

no

Results: F1 generation

General toxicity (F1)

Clinical signs:

not examined

Dermal irritation (if dermal study):

not examined

Mortality / viability:

mortality observed, non-treatment-related

Description (incidence and severity):

In the 1st F1 litter, at 0 mg/kg bw/day, the 21 day survival rate was 93%; at 200 mg/kg bw/day it was 92%.

In the 2nd F1 litter, at 0 mg/kg bw/day, the 21 day survival rate was 49%; at 200 mg/kg bw/day it was 66%.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Anogenital distance (AGD):

not examined

Nipple retention in male pups:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

Ethyl maltol had no effect on fetal development

Histopathological findings:

not examined

Developmental neurotoxicity (F1)

Behaviour (functional findings):

not examined

Developmental immunotoxicity (F1)

Developmental immunotoxicity:

not examined

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

>= 2 000 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: highest dose tested

Target system / organ toxicity (F1)

Critical effects observed:

no

Overall reproductive toxicity

Reproductive effects observed:

no

Applicant's summary and conclusion

Conclusions:

In a One Generation Reproductive Toxicity/Combined Chronic Toxicity & Carcinogenicity Study in Charles River rats with Ethyl Maltol, the NOAEL (parental, offspring) was ≥200 mg/kg bw/day.

Executive summary:

In a one generation reproductive toxicity/combined chronic toxicity & carcinogenicity study (Gralla et al., 1969), Ethyl Maltol was administered to 4 groups of Charles River male and female rats (25/sex/group) in the diet at dose levels of 0, 50, 100 and 200 mg/kg bw/day daily for 2 years. Between 15 and 21 and 30 and 36 weeks, 10 males and 10 females per level were mated to produce two separate litters.

All dose levels of ethyl maltol were well tolerated throughout the 2-year feeding period. The test and control animals grew and maintained the body weight in a comparable manner. After two years on test, one control rat had a massive anemia of unknown etiology. Otherwise, all hematologic values for test and control animals were within normal ranges. All rats showed a tendency toward albuminuria; otherwise, urinalysis values were essentially normal. Pathologic changes consistent with aged rats were observed primarily in the pulmonary, endocrine, urinary, and cardiovascular systems. Neoplasia occurred in a random manner with no apparent relationship between number, location, or type of tumors and treatment.

A fall in fertility was noted in test and control groups at the second mating but controls were affected also (60% conception at 200 mg/kg bw/day, 50% conception for controls). This was due presumably to the advanced age of the animals. Ethyl maltol had no effect on gestation, parturition or lactation.

Ethyl maltol had no effect on fetal development and no gross internal abnormalities were noted. In the 1st F1 litter, at 0 mg/kg bw/day, the 21 day survival rate was 93%; at 200 mg/kg bw/day it was 92%. In the 2nd F1 litter, at 0 mg/kg bw/day, the 21 day survival rate was 49%; at 200 mg/kg bw/day it was 66%. There was no difference in the average weight of pups at 21 days lactation between controls and treated groups.

The EFSA peer-reviewed NOAEL (parental/offspring) was ≥200 mg/kg bw/day.