Registration Dossier

Toxicological information

Repeated dose toxicity: oral

Currently viewing:

Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report Date:
2000

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: KANPOGYO No.700, YAKUHATSU No. 1039.61, and KIKYKU No. 1014.
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Dipropylene glycol methyl ether (DPGME)
- Physical state: Colorless transparent liquid
- Analytical purity: 99%
- Storage condition of test material: The test substance was stored in a cabinet at ambient temperature.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
Source: Charles River Japan Inc.
- Age at study initiation: 6-7 weeks
- Weight at study initiation: Male: 208 to 235 gms and Female: 140 to 169 gms
- Fasting period before study:
- Housing:
- Diet (ad libitum): A pelleted laboratory rodent diet autoclaved CRF-1
- Water (ad libitum): Tap water irradiated with the ultraviolet light
- Acclimation period: 10 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 23 °C
- Humidity (%): 30-70%
- Air changes (per hr): 20
- Photoperiod: (12 hrs dark /12 hrs light):


IN-LIFE DATES: From: 2000-01-11 To: 2000-05-10

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: Water for injection
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: Test substance was diluted with water for injection to 0.4 %, 2 % and 10 % concentration which were equivalent to the 40, 200 and 1000 mg/kg respectively. Formulation was prepared freshly each day
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
Not specified in the report
Duration of treatment / exposure:
4 weeks
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
40 mg/kg
Basis:
nominal in water
Remarks:
Doses / Concentrations:
200, mg/kg
Basis:
nominal in water
Remarks:
Doses / Concentrations:
1000 mg/kg
Basis:
nominal in water
No. of animals per sex per dose:
5/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: 2 weeks (controls and high dose)
Positive control:
None

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed three times daily (immediately before and after administration and 1 to 2 hour after administration later from the treatment) for clinical signs.

BODY WEIGHT: Yes
- Time schedule for examinations: All the rats were weighed on the first day of administration, twice a week during treatment and recovery period, on the day before necropsy and on the day of necropsy.


FOOD CONSUMPTION: Food consumption of all rats were measured weekly for 2 days and daily food intakes were calculated.
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

FOOD EFFICIENCY: Not examined
WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No
OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: During necropsy
- Anesthetic used for blood collection: Yes (identity) : Ether
- Animals fasted: No
- How many animals: 20 male and 20 female for regular dose levels and 10 male +10 female for recovery group
- Parameters checked in table [No.5-1 and 5-2] were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: During necropsy
- Animals fasted: No
- How many animals: 20 male and 20 female for regular dose levels and 10 male +10 female for recovery group
- Parameters checked in table [No.6-1 and 6-2] were examined.


URINALYSIS: Yes
- Time schedule for collection of urine: During 4th week of administration and 2nd week of recovery period.
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Parameters checked in table [No.4-1, 4-2, 4-3, 4-4] were examined.


NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All surviving animals were fasted from the evening at the end of treatment period or at the end of recovery period. On the next day animals were examined by bleeding from the abdominal aorta under anesthesia for necropsy and the organs and tissues were macroscopically.
HISTOPATHOLOGY: Yes
As to the autopsied animals, eyes (Including optic nerve) were preserved in Davidson's fixative and following tissues were preserved in 10 % buffered formalin. Brain, pituitary, thyroids, heart, thymus, trachea and lung (fulfilled with the fixative), liver, spleen, esophagus, stomach, duodenum, ileum, colon, kidneys, adrenals, urinary bladder, testes, epididymides, prostrate, ovaries, uterus, femoral bone, spinal cord, sciatic nerve and lymph nodes.
Other examinations:
Organ weights: The following organs from each animal autopsied were dissected and weighed. Relative organ weight to body weight was calculated. Brain, heart, thymus, liver, kidneys, spleen, adrenals, testes, epididymides and ovaries.
Statistics:
As to quantative data the Bartlett’s test was applied to test for heterogeneity of variance between treatments. If no significant heterogeneity was detected, a one way analysis of variance was carried out. If significant heterogeneity was detected then analysis was followed by Dunnet to compare the control and treatments. If significant hetrogeneity of variance was present, the Krushkal -Wallis analysis of ranks was used. Statistical analysis was performed on two sides tests at 5 % and 1 % level of significance.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY: All animals were survived during the treatment period of 28 days and 2 weeks of recovery period. Salivation was noted immediately after daily treatment in the 9 male and 3 female animals treated with the 1000 mg/kg from day 11 onward. However, this sign disappeared within 1 to 2 hours from the treatment and it seems to be a temporal change. There were sporadic incidence of soft stool, muddy stool but there was no difference of incidence between the groups. There was no change in all animals of recovery group.

BODY WEIGHT AND WEIGHT GAIN: There were no significant differences between control group and treatment groups for body weights.

FOOD CONSUMPTION: There were no significant differences between control group and treatment groups for food consumption. For recovery group in the first week there was statistically higher value was noted in the male treated with the 1000 mg/kg dose group but it disappeared in the second week.

HAEMATOLOGY: In the 28 day treatment group, MCHC were recorded statistically significant in 200 mg/kg dose level as compare to controls but there was no statistical significance in the animals treated with 1000 mg/kg dose level. The above change found in 200 mg/kg was not related to the dose levels. There were no other changes in the parameters determined.
In the recovery group statistically significant higher Ht and Hb concentrations were noted in the female animals treated with 1000 mg/kg. However, differences from the control were always small. There were no other changes in the parameters determined.

CLINICAL CHEMISTRY: In the 28 day treatment group, chloride level was statistically significantly higher than control for rats treated with 40 mg/kg and for male rats treated with 200 and 1000 mg/kg. Additionally, a statistically significantly lower Alb and Glb in ration than control was noted in female rats treated with 200 and 1000 mg/kg.There were no other changes in the parameters determined.
In recovery group statistically significantly higher glucose and total glyceride value were noted in the male animals treated with 1000 mg/kg while female animals treated with 1000 mg/kg showed statistically significantly lower Alb/Glb in ration and total bilirubin values. However, these differences from control were also small. There were no other changes in the parameters determined.

URINALYSIS: In the 28 day treatment group, there were no differences from control in urinalysis in any of the treatment groups. In recovery group statistically lower potassium value was noted in female animals treated with the 1000 mg/kg but this extent of difference was small and there were no other parameters to show the difference with those of the control.

ORGAN WEIGHTS: In the 28 day treatment group, statistically significantly higher relative liver weights were noted in the male and female animals treated with 1000 mg/kg. Absolute and relative liver weights in the groups treated with more than 200 mg/kg showed a tendency of increases in the relation with the dose levels, while animals treated with 40 mg/kg showed the similar level of liver weight as in control animals. Statistically significantly lower relative heart weight was noted for the male animals treated with 40 or 200 mg/kg but there was no significant increase in the animals treated with 1000 mg/kg and there was no dose relationship for this change. There were no other parameters to show the difference with those of the control.
In recovery group, statistically significantly higher relative liver weight was noted in the male animals treated with 1000 mg/kg. There was also the relatively higher value of liver weight for female animals at same dose group but without statistical significant. There were no other differences in the absolute and relative organ weight from control.

GROSS PATHOLOGY: Macroscopic examination performed at 28 days treatment and recovery period revealed no changes in the animals of the treatment attributable to treatment with this test substance.

HISTOPATHOLOGY: NON-NEOPLASTIC: In the 28 day treatment group, centrilobular hypertrophy was noted in the livers of two animals treated with the 1000 mg/kg but there was no change in the groups treated with less than 200 mg/kg.Slight to moderate grade of the eosinophil bodies were noted in the proximal tubules of each one male treated with 40 or 1000 mg/kg. In addition to above findings, aggregation of mononuclear cells of slight degree were noted in the liver of two control female animals and two 1000 mg/kg male animals. Slight degree of regeneration of renal tubules was noted in the one male each of control, 200 mg/kg and 1000 mg/kg animal and one slight degree of aggregation of mononuclear cells was noted in one male control animal.Extramedually hematopoiesis of spleen was noted in all animals of control and animals treated with 1000 mg/kg which was slight to moderate degree. In one male animal of the control, there was a slight degree of epithelial abruption in seminiferous tubules. Slight to moderate degree of cell infiltration of mononuclear cells in epididymides and prostate was noted in one male each of control and 1000 mg/kg group. Slight degree of aggregation of foamy cells in lung was noted in a female treated with 1000 mg/kg.

In recovery groups, slight degree of centrilobular hypertrophy in liver was noted in two male animals treated with 1000 mg/kg.Moderate to severe degree of eosinophilic bodies in proximal tubules was noted in the two male animals treated with 1000 mg/kg. Aggregation of mononeulaer cells of slight degree were noted in the liver of one control male and two control females animals and four 1000 mg/kg male animals and two 1000 mg/kg female animals. One male animal of control showed a slight degree of vacuolation and one female animal of control showed a slight degree of focal vacuolation.Slight degree of regeneration of renal tubules was noted in the one male of control and two male treated with 1000 mg/kg and one slight degree of infiltration of mononuclear cells was noted in one male animal treated with 1000 mg/kg. Extramedually hematopoiesis of spleen was noted in all animals of control and animals treated with 1000 mg/kg which was slight degree. Slight degree of infiltration of mononuclear cells in urinary bladder was noted in one male treated with 1000 mg/kg.Slight to moderate degree of infiltration of mononuclear cells in prostate was noted in the two control animals and two animals treated with 1000 mg/kg.Slight degree of aggregation of foamy cells in lung was noted in one male treated with 1000 mg/kg. Slight degree of cyst in pituitary was noted in one male treated with 1000 mg/kg.




Effect levels

open allclose all
Dose descriptor:
NOEL
Effect level:
200 other: mg/kg
Sex:
male/female
Basis for effect level:
other: overall effects
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: tentative salivation, increased relative liver weight accompanied by centrilobular hypertrophy

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

The liver weight increase observed at the highest dose level was only slight and no histopathologic changes, except for hypertrophy, accompanied this effect. There were no changes in clinical chemistry (ALP, ASP) indicating a liver damage. The same effect was observed with other structurally related molecules, e.g. propylene glycol methyl ether has been shown to cause liver weight increases via a phenobarbital-like enzyme induction mode of action and it is highly likely that dipropylene glycol methyl ether acetate liver weight increases occur via the same mode of action. As this is an adaptive effect typical for many glycol ethers, it is not consered as adverse.

Applicant's summary and conclusion

Conclusions:
Based on the results of this study a no observed adverse effect level (NOAEL) of 1000 mg DPM/kg-day and a no observed effect level (NOEL) of 200 mg/kg/dayc an be established in rats under the conditions of this study.
Executive summary:

This study was performed to assess the systemic toxicity of dipropylene glycol methyl ether (DPGME) to the rat by oral administration, once daily for 28 days, to 3 groups of 5 male and 5 female rats at dosage levels of 40, 200 and 1000 mg/kg/day. A negative control group was provided. A recovery group of 5 males and 5 females were additionally assigned to the control group and high dose group.

All animals survived during the treatment period of 28 days and the 2 weeks recovery period. There were no significant differences between control group and treatment groups for body weights and food consumption. Macroscopic examination performed at the end of the 28 days treatment and the recovery period revealed no treatment-related changes.

Tentative salivation was recorded in the male and female animals treated with the 1000 mg/kg from the day 11 onward, which appeared immediately after oral administration of test substance. Relative liver weight of male and female animals treated with the 1000 mg/kg at 28 days treatment increased with statistical significance, while the male animals treated with 1000 mg/kg at recovery group showed also a statistical significant increases in absolute and relative livery weight. Upon histopathological examination centrilobular hypertrophy of the liver was observed in the animals treated with 1000 mg/kg.

There were no other changes that were considered to be related to treatment of this test substance.

It is concluded that 200 mg/kg/day represents the no-observed-effect level (NOEL) and that 1000 mg/kg/day represents no-observed-adverse-effect level (NOAEL)for DPGME in the rat. The only effects observed at 1000 mg/day were transient salivation immediately after administration of the test material, increased liver weight and centrilobular hypertrophy of the liver. The liver weight increase (which was very minor, <10 %) and hypertrophy in the liver observed at 1000 mg/kg/day was likely due to increased metabolism and was not accompanied by an increase in liver enzymes.