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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
February 23, 2000 - August 29, 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to OECD TG 408 and in accordance with the principles of GLP.
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

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

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Version / remarks:
also EEC Part B.26, 87/302/EEC, Japanese MITI (Subchronic Oral Study) and USEPA-OPPTS 870.3100
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Purity of the test material determined by gas chromatography(GC) using flame ionization detector (FID) was 99.3%. The structure was confirmed by nuclear magnetic resonance (NMR). Water content was 0.01% by the Karl Fisher method.

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
Animals were obtained from Charles River Laboratories Inc. (Raleigh, NC) and were 7 weeks old at the start of the study. The animals were uniquely identified and housed two to three per cage (acclimation period) or one per cage (study) in stainless steel wire cages in a room maintained at 21.5 -22.2 degrees C, 48.5 -51.9% relative humidity and a 12 hour light/12 hour dark cycle. Room air was exchanged 12-15 times per hour. Animals were provided Purina Certified Rodent Lab Diet #5002 (Purina Mills, Inc., St. Louis, MO) and tap water ad libitum. There were no contaminants that could adversely affect the study. Rats were acclimated for 15 days prior to the start of the study, stratified according to body weight and randomly assigned to groups. Animals chosen for use were considered by a veterinarian to have adequate health.

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Four groups of Fischer 344 rats (10/sex/dose level) received test material in their drinking water at concentrations equivalent to target doses of 0, 50, 150 or 500 mg/kg-day for 13 weeks. Drinking water solutions were prepared weekly. The amount of test material administered was adjusted weekly based on the most recent body weights and water consumption data.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
According to the MSDS, the test material is totally miscible in water at concentrations up to 17.5% (25 degrees C), approximately twice the concentration of the high dose for the study. Therefore, a homogeneity analysis was not performed. Samples of water from the first female in the low dose group and the first male in the high dose group were taken during week one for stability analysis. The material was shown to be stable in water for at least 8 days. Analysis of all dose levels (HPLC with UV detection and external standards) was conducted during Weeks 1, 8 and 13 (concentrations were 90 - 108% of target).
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
continuous
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 50, 150 or 500 mg/kg bw
Basis:
nominal in water
No. of animals per sex per dose:
10
Control animals:
yes, concurrent no treatment
Details on study design:
The high-dose level of 500 mg/kg/day was chosen based on results of the 2-week drinking water study and was expected to produce increased liver weights. The remaining dose levels were expected to provide dose-response data for any treatmentrelated effect(s) observed in the high-dose group. The low-dose was also expected to be a no-observed-effect level (NOEL).
Positive control:
None

Examinations

Observations and examinations performed and frequency:
Rats were observed for clinical signs of toxicity prior to the start of the study and twice daily thereafter. A detailed clinical observation was conducted pre-exposure and weekly during the study. Functional testing (sensory evaluation, rectal temperature, grip performance and motor activity) was conducted predosing and during the last week of the study. Body weights and feed and water consumption were measured during the pre-exposure period and once per week during the study. Ophthalmological examinations were conducted by a veterinarian prior to treatment and at termination. Urinalyses were conducted on urine collected (16 hours in metabolism cages) one week prior to termination.
Sacrifice and pathology:
Standard hematology and clinical chemistries and a prothrombin time analysis were performed on blood collected form the orbital sinuses of anesthetized animals at termination (after an overnight fast). At termination, all animals were euthanized and subjected to complete necropsy. The eyes were examined in situ by application of a moistened glass slide to each cornea. The brain, liver, kidneys, heart, adrenals, testes, epididymides, uterus, ovaries, thymus and spleen were weighed. The adrenals, aorta, auditory sebaceous glands, bone, bone marrow, brain, cecum, cervix, coagulating glands, colon, duodenum, epididymides, esophagus, eyes, gross lesions, heart, ileum, jejunum, kidneys, lacrimal/Harderian glands, larynx, liver, lungs, mammary gland, mediastinal lymph node and tissues, mesenteric lymph node and tissues, nasal and oral tissues, ovaries, oviducts, pancreas, parathyroid gland, peripheral nerve, pituitary, prostate, rectum, salivary glands, seminal vesicles, skeletal muscle, skin and subcutis, spinal cord, spleen, stomach, testes, thymus, thyroid gland, tongue, trachea, urinary bladder, uterus and vagina were collected from all animals and preserved. All tissues collected from control and high dose animals were examined histologically. The lungs, liver, kidneys and relevant gross lesions (with the exception of a fractured tail) from the other groups also were examined histologically.
Other examinations:
None
Statistics:
All data were first tested for equality of variance using Bartlett's test (alpha (a) = 0.01). If the results from the test were significant, then data were transformed (common log, inverse or square root) to obtain equality of variances. Motor activity counts were reported as square roots. Body weights were evaluated using a repeated measures analysis of variance (ANOVA) for time, sex and dose. If the test was significant (a = 0.02) the analysis was repeated separately for each sex. The time-dose interaction was examined next. If significant (a = 0.05), linear contrasts tested this interaction for each dose group (compared to control). A Bonferroni correction was applied to control the experiment-wise error rate. Final body weight, organ weight (excluding sex organs), hematology (excluding RBC indices and differential WBC), clinical chemistry and urine specific gravity data were evaluated using a two-way ANOVA with the factors of sex and dose. If the sex-dose interaction was significant (a = 0.05), a one-way ANOVA was performed for each sex. Weights of sex organs were analyzed using a one-way ANOVA. Comparisons of data (to control) were made with Dunnett's test when a significant dose effect (a = 0.05) was identified. Water and feed consumption data were evaluated by a Bartlett's test for equality of variances (a = 0.01), followed by a parametric ANOVA and a Dunnett's test (if significant at a = 0.05). Descriptive statistics were reported for body weight gains, RBC indices and WBC differential counts. Outliers were identified by a sequential test (a = 0.02), and excluded from feed consumption evaluations. Rectal temperature and grip performance data were analyzed by a factorial analysis of covariance (ANCOVA) with the factors of sex and dose and the covariate of the pre-exposure value. Motor activity data were analyzed by a factorial repeated-measures design with factors of sex, treatment and time. DCO incidence scores were analyzed by a Z-test.

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):
effects observed, treatment-related
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
500 mg/kg bw: Increased absolute and relative liver weight in males (16%), decreased water consumption in females (10% reduction), decreased urine volume in males (3.9 +/-0.6 ml vs. 4.6 +/- 0.7 ml in control) and females (3.8 +/- 3.7 ml vs. 5.3 +/- 3.5 ml in control), increased urine specific gravity for females (1.079 +/- 0.022 vs. 1.059 +/- 0.018), and increased cholesterol in males (by 17%) were considered to be related to treatment. Three males had livers which appeared increased in size. One male and one female had hemolyzed blood in the lumen of the stomach. Slightly lower alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in males and females, higher relative kidney and adrenal weights of males and females and higher absolute and relative kidney weights of males and females were not considered to be treatment-related or toxicologically relevant. No histopathological changes were noted that could be attributed to the test material. This was considered to be the NOAEL for males by the study investigator. It was not considered to be the NOAEL for females based on the decreased water consumption and urine volume and increased urine specific gravity.

150 mg/kg bw: Lower ALT in males and females and higher absolute and relative thymus weights of males were not considered to be biologically significant. One male had hemolyzed blood in the lumen of the stomach. No histopathological changes were noted that could be attributed to the test material. This was considered to be the NOEL for males and females by the study investigator.

50 mg/kg/day: No effect of treatment

Effect levels

open allclose all
Dose descriptor:
NOEL
Effect level:
150 mg/kg bw/day (nominal)
Sex:
male/female
Dose descriptor:
NOAEL
Effect level:
500 mg/kg bw/day (nominal)
Sex:
male
Basis for effect level:
other: The NOAEL for females was not listed in the report, and is considered by the reviewer to be the NOEL of 150 mg/kg bw.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

The authors concluded that the differences in liver weight and cholesterol were likely due to induction of organelles required for metabolism of the test material and altered lipid metabolism (respectively) and were not toxicologically significant. Alterations in urinary parameters for females were attributed to decreased water consumption.

Applicant's summary and conclusion

Conclusions:
Based on the subchronic study results for dipropylene glycoln-propyl ether, the no-observed-adverse-effect level (NOAEL) for male Fischer 344 rats was the targeted concentration of 500 mg/kg/day while the no-observed-effect level (NOEL) for males and females was 150 mg/kg/day.
Executive summary:

Four groups of 10 male and 10 female Fischer 344 rats were given drinking water solutions supplying 0, 50, 150, or 500 mg Dipropylene glycol n-propyl ether (DPnP)/kilogram body weight/day (mg/kg/day) for 13 weeks to evaluate the potential for systemic toxicity. Standard toxicologic parameters were evaluated.

 

Treatment-related effects consisted of 1) an increased absolute and relative liver weight for males given 500 mg/kg/day, 2) decreased water consumption for females given 500 mg/kg/day, 3) decreased urine volume in males and females given 500 mg/kg/day, 4) increased urine specific gravity for females given 500 mg/kg/day, and 5) an increase in cholesterol of males given 500 mg/kg/day.

 

The differences in liver weight and cholesterol were likely due to the induction of organelles required for the metabolism of DPnP and altered lipid metabolism, respectively, and were not toxicologically significant. Alterations in urinary parameters for females were directly attributed to decreased water consumption.

 

The no-observed-adverse-effect level (NOAEL) for male Fischer 344 rats was the targeted concentration of 500 mg/kg/day. The no-observed-effect level (NOEL) for males and females was 150 mg/kg/day.