Residues (petroleum), heavy coker gas oil and vacuum gas oil

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian cell study: DNA damage and/or repair

Remarks:

Type of genotoxicity: DNA damage and/or repair

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Near-guideline, GLP-compliant study. Adequate for assessment.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.39 (Unscheduled DNA Synthesis (UDS) Test with Mammalian Liver Cells In Vivo)

Principles of method if other than guideline:

Test substance administered by oral gavage to male rats 2 hr and 12 hr prior to sacrifice. Liver excised, and uptake of 3H-thymidine by primary cultures in vitro used to quantify unscheduled DNA synthesis

GLP compliance:

yes

Type of assay:

unscheduled DNA synthesis

Test material

Test material information

Constituent 1

Reference substance name:

64741-62-4

Cas Number:

64741-62-4

IUPAC Name:

64741-62-4

Test material form:

other: Viscous hydrocarbon liquid

Details on test material:

Catalytic cracked clarified oil (CCCO), API 81-15, CAS No. 64741-62-4.
Dark brown viscous liquid

Data below taken from American Petroleum Institute (1985d). In-vivo sister chromatid exchange (SCE) assay. Catalytic cracked clarified oil, API Sample 81-15, CAS No. 64741-62-4. Testing laboratory: Microbiological Associates Inc., 5221 River Road, Bethesda, MD 20816, USA. Owner company: American Petroleum Institute, 2101 L Street, Northwest, Washington, DC 20037, USA. Study number: 32-32754. Report date: 1985-11-25.

Gravity API: 0.1
Specific gravity: 1.0753
Viscosity in SUS @ 210 °F: 56.1
Flash Point °F: 396
Sulfur wt %: 1.1
Pour Pt °F: 35
Asphaltenes % (MN 596): 4.2
Carbon residue wt %: 4.6
Ash wt %: 0.05

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hilltop Animal Supply, Chatswoth, CA USA
- Weight at study initiation: 233-363 g

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

gavage administration in corn oil, single treatment, 2 hr and 12 hr prior to sacrifice

Duration of treatment / exposure:

2 hr or 12 hr prior to sacrifice

Frequency of treatment:

1 dose given on one day

Post exposure period:

not applicable

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 50, 200 and 1000 mg/Kg bw
Basis:
nominal conc.

No. of animals per sex per dose:

Vehicle control, positive control: 5
Treatment groups: 3

Control animals:

yes, concurrent vehicle

Positive control(s):

2-acetylaminofluorene, 50 mg/Kg bw

Examinations

Tissues and cell types examined:

Primary hepatocyte cultures prepared following in vivo exposure

Details of tissue and slide preparation:

DETAILS OF SLIDE PREPARATION:
Primary liver cells were attached to coverslips and incubated in medium containing tritiated thymidine prior to fixing and mounting on slides. Kodak NTB-2 emulsion with methyl green Pyronin K counterstain was used to visualise nuclei.

METHOD OF ANALYSIS:
50 morphologicaly unaltered cells per slide were selected at random and subject to autoradiographic counting. Background counts (for cytoplasm) were subtracted from the nuclear counts to give net grains per nucleus. The percentage of cells in repair was calculated as those cells with at least 5 net grain per nucleus.

A minimum of 3 slides was scored for each of 3 animals i.e. 450 cells/dose/time point examined.

Evaluation criteria:

A positive result was characterised by one or more of the following:
- presence of a dose response
- changes in frequency distribution of cellular response
- increase in the percentage of cells in repair

Statistics:

No statistical methods used

Results and discussion

Test results

Sex:

male

Genotoxicity:

positive

Remarks:

200 mg/Kg bw given 12 hr pre-sacrifice; 1000 mg/Kg bw/d given 2 or 12 hr pre-sacrifice

Toxicity:

not examined

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Any other information on results incl. tables

The results were positive at 200 mg/Kg (after 12 hours but not after 2 hours) and at 1000 mg/Kg (after both 2 and 12 hours).

In this assay on primary rat liver cultures, unscheduled DNA synthesis (UDS) in the test groups, as measured by the amount of incorporated tritiated thymidine, was significantly elevated, in a dose-dependent manner, above the level found in the negative control group treated with corn oil alone.

The positive control group gave the expected results.

Percentage of cells in repair:

Treatment	Time between dosing and sacrifice
	2 hr	12 hr
0 mg/Kg bw	-	3%
50 mg/Kg bw	1%	1%
200 mg/Kg bw	1&	16%
1000 mg/Kg bw	14%	58%
2-aminofluorene	-	87%

- = not done

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): positive
The test substance induced unscheduled DNA repair in rat liver following single oral administration.

Executive summary:

The potential of catalytic cracked clarified oil to induce unscheduled DNA repair in rat liver was investigated in vivo in a near guideline GLP-compliant study. Animals received a single oral gavage treatment of 0 (corn oil), 50, 200 or 1000 mg test substance /Kg bw/d 2 or 12 hr prior to sacrifice, with positive controls given a single oral treatment of 0 or 50 mg/Kg 2-aminofluorene. Following incubation in medium containing tritiated thymidine, isolated primary liver cells from treated animals showed a net increase in the percentage of cells undergoing repair relative to the controls; a satisfactory response was obtained in the positive control group.

The results demonstrated that test substance had a clear potential to induce unscheduled DNA synthesis in rat liver in vivo.