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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Start date Jan 11 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Generally comparable to a guideline study.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report Date:
1998

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Principles of method if other than guideline:
The study was conducted according to MacGregor et al. (Fundam. Appl. Toxicol Vol 114:513-522, 1990) and many of the experimental details provided in this endpoint summary are taken from that publication. The mice used in this study were taken from a repeated dose inhalation study reported in Section 7.5.3 of this file.
GLP compliance:
not specified
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material: tetrahydrofuran- Supplier: ChemCentral, Kansas City, MO, USA- Physical state: clear, colorless liquid- Analytical purity: approximately 99% (determined by elemental analysis)- Impurities: none identified greater than 0.1%- Purity test date: not provided- Lot/batch No.: lot WK8-6-86- Expiration date of the lot/batch: not provided- Stability under test conditions: stability studies indicated that tetrahydrofuran was stable as the bulk chemical for 2 weeks when stored protected from light at temperatures up to 25 deg C. Stability was monitored during the 14-week studies and no degradation of the bulk chemical was detected.- Storage condition of test material: at room temperature in the original metal containers under a nitrogen blanket- Other: Karl Fischer analysis indicated less than 0.06% water; peroxide concentrations were no greater than 3 ppm

Test animals

Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS- Source: Simonsen Laboratories, Inc., Gilroy, CA- Age at study initiation: 7 weeks (average)- Weight at study initiation: not available- Fasting period before study: No- Housing: Stainless-steel wire-bottom (Hazleton Systems, Inc., Aberdeen, MD), 1 animal/cage.- Diet: NIH-07 Open Formula Pelleted feed, ad libitum except during exposures- Water: Tap water (City of Richland municipal supply), ad libitum- Acclimation period: quarantined 15 days before the beginning of the studiesENVIRONMENTAL CONDITIONS (Exposure Chambers)- Temperature: 19.6 to 26.6 °C- Humidity (%): 29 to 75- Air changes (per hr): 15 +/- 3- Photoperiod (hrs dark / hrs light): 12/12IN-LIFE DATES: From: 12 February 1987 To: 15 May 1987

Administration / exposure

Route of administration:
inhalation: vapour
Vehicle:
Unchanged (no vehicle)
Details on exposure:
Vapor Generation/Exposure System:Tetrahydrofuran vapor was generated with a rotary evaporation system (Buchi Rotavapor, Model EL-131S, Buchi Laboratories Technik AG, Flavil, Switzerland). The vapor entered a short distribution manifold from which individual delivery lines carried metered amounts of the vapor to each exposure chamber. At equilibrium, each valve was opened to allow flow to chambers. At each chamber location, the vapor was injected into the chamber duct after dilution with an appropriate amount of charcoal- and HEPA-filtered chamber air to achieve the desired chamber concentration.The exposure system consisted of stainless-steel chambers designed at Batelle Northwest Laboratories (Hazelton 2000, Aberdeen, MD).
Duration of treatment / exposure:
14 weeks
Frequency of treatment:
6 hours plus T90 (12 minutes) per day, 5 days/week
Post exposure period:
None
Doses / concentrations
Remarks:
Doses / Concentrations:0 (chamber control), 66, 200, 600, 1800 and 5000 ppm Basis:nominal conc.
No. of animals per sex per dose:
10
Control animals:
yes, concurrent no treatment
Positive control(s):
No

Examinations

Tissues and cell types examined:
Peripheral blood samples were obtained from male and female mice and smears immediately fixed. Slides were scanned at 630 or 1,000X magnification with a semiautomatic image analysis system to determine the frequency of micronuclei in 2,000 polychromatic erythrocytes (PCEs) and 10,000 normochromatic erythrocytes (NCEs) in up to 10 animals/exposure group.
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: Animals dosed at 0 (chamber controls), 600, 1800 or 5000 ppm for 14 weeks in an inhalation toxicity test were chosen for this assay.TREATMENT AND SAMPLING TIMES:Immediately following the 14-week inhalation exposures, peripheral blood was obtained from male and female mice.DETAILS OF SLIDE PREPARATION:Peripheral blood was obtained from the ventral tail vessel. Smears from peripheral blood samples were immediately prepared and fixed in absolute methanol for about 2 minutes. Methanol-fixed slides were stained with Hoechst 33258/pyronin Y double fluorescent stain using Sorensen’s M/15 phosphate buffer.METHOD OF ANALYSIS: Slides were scored at 630X under oil-immersion microscopy. The incidence of micronucleated PCEs was scored for each animal. The polychromatic to normochromatic cell ratio was based on the number of PCEs noted in the first 100 normochomatic erythrocytes (NCEs). If no PCEs were seen in the first 100 NCEs, an automated system for counting 10,000 cells was employed and the slide was not scored if the ratio was less than 0.5%.
Evaluation criteria:
An individual trial was considered positive if the trend test P value was
Statistics:
The results were tabulated as the mean of the pooled results from all animals within a treatment group plus or minus the standard error of the mean. The frequency of micronucleated cells among NCEs and PCEs were analyzed by a statistical software package that tested for increasing trend over exposure groups with a one-tailed Cochran-Armitage trend test, followed by pairwise comparisons between each exposed group and the control.

Results and discussion

Test resultsopen allclose all
Sex:
male
Genotoxicity:
negative
Remarks:
micronucleated cells/1000 PCE cells
Vehicle controls validity:
valid
Sex:
male
Genotoxicity:
ambiguous
Remarks:
micronucleated cells/1000 NCE cells, trend test P = 0.074
Vehicle controls validity:
valid
Sex:
female
Genotoxicity:
negative
Remarks:
micronucleated cells/1000 PCE cells
Vehicle controls validity:
valid
Sex:
female
Genotoxicity:
negative
Remarks:
micronucleated cells/1000 NCE cells
Vehicle controls validity:
valid

Any other information on results incl. tables

The frequency of micronuclei in mouse peripheral blood erythrocytes following treatment with tetrahydrofuran by inhalation for 14 weeks is presented in the following table.

         Micronucleated Cells/1000 Cells   
  Treatment   Dose (ppm)   Number of Mice Scored  PCEs  NCEs  Significance
 Male          
 Chamber control   10  1.50 +/- 0.29 1.18 +/- 0.09   
 Tetrahydrofuran  600  10  1.69 +/- 0.25 1.27 +/- 0.10   
   1800  10 1.79 +/- 0.22  1.58 +/- 0.08*   
   5000  7 1.47 +/- 0.27  1.41 +/- 0.13 

P = 0.297 (PCEs)

P = 0.074 (NCEs) 

 Female   10   1.85 +/- 0.38  1.43 +/- 0.18  
 Chamber control  600 10  1.01 +/- 0.24  1.16 +/- 0.07  
 Tetrahydrofuran  1800 10  1.34 +/- 0.31  1.15 +/- 0.07   
   5000 10  1.29 +/- 0.19  1.18 +/- 0.08 

P = 0.297 (PCEs)

P = 0.074 (NCEs)

* Significantly different from control (P=0.004)

Significance tested by the one-tailed trend test; P < 0.025

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negativeIn female mice, the frequencies of micronucleated cells in polychrmatic or normochromatic erythrocytes were not increased. In male mice, a small increase in the frequency of micronucleated normochromatic erythrocytes was concluded to represent an equivocal response. No significant increase was seen in polychromatic erythrocytes.
Executive summary:

The frequencies of micronucleated erythorcytes were determined in peripheral blood samples obtained from male and female mice dosed by inhalation at 0 (chamber control), 600, 1800 or 5000 ppm in 14 -week inhalation toxicity studies. With the exception of an equivocal response in male mice represented as an increased frequency of micronucleated normochromatic cells (P = 0.074), tetrahydrofuran failed to produce a positive response in female mice based on micronucleated polychromatic or normochromatic erythrocytes or a positive response in male mice based on micronucleated polychromatic erythrocytes.