Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro DNA damage and/or repair study

Remarks:

Type of genotoxicity: DNA damage and/or repair

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From Aug to Sep 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Mutation Research 123: 363-410

Deviations:

no

GLP compliance:

yes

Type of assay:

DNA damage and repair assay, unscheduled DNA synthesis in mammalian cells in vitro

Test material

Test material information

Constituent 1

Reference substance name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

EC Number:

601-490-4

Cas Number:

117704-25-3

Molecular formula:

C50H74O14

IUPAC Name:

(1'R,2S,4'S,5S,6R,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-6-cyclohexyl-21',24'-dihydroxy-12'-{[(2R,4S,5S,6S)-5-{[(2S,4S,5S,6S)-5-hydroxy-4-methoxy-6-methyloxan-2-yl]oxy}-4-methoxy-6-methyloxan-2-yl]oxy}-5,11',13',22'-tetramethyl-5,6-dihydro-3',7',19'-trioxaspiro[pyran-2,6'-tetracyclo[15.6.1.1⁴,⁸.0²⁰,²⁴]pentacosane]-10',14',16',22'-tetraen-2'-one

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

Batch No.: 15497-41-2
Purity: Not specified

Method

Species / strain

Species / strain / cell type:

hepatocytes: rat

Test concentrations with justification for top dose:

Preliminary cytotoxicity test: 10.0, 20.0, 40.0, 60.0, 80.0, 100.0 and 200.0 μg/mL;
Definitive test: 1.7, 5.0, 7.5, 10.0, 15.0, 20.0 μg/mL

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: The primary choice of solvent is an aqueous solvent (culture medium or saline) due to their non-toxic properties in mammalian cultures. An alternative choice is a non-toxic concentration of an organic solvent such as dimethylsulfoxide (DMSO) or ethyl alcohol (ETOH).

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

no

Remarks:

Preliminary cytotoxicity test

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-acetylaminofluorene

Remarks:

Definitive test

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Preincubation period:
- Exposure duration: Preliminary cytotoxicity test: 18-20 hours; Definitive test: 18-20 hours
- Expression time (cells in growth medium):
- Selection time (if incubation with a selection agent):
- Fixation time (start of exposure up to fixation or harvest of cells): 10 mins

SELECTION AGENT (mutation assays):
SPINDLE INHIBITOR (cytogenetic assays):
STAIN (for cytogenetic assays): trypan blue

NUMBER OF REPLICATIONS: Preliminary cytotoxicity test: duplicate; Definitive test: four

NUMBER OF CELLS EVALUATED: Preliminary cytotoxicity test: At least one hundred attached cells; Definitive test: One culture from each treatment group counted at least 100 attached cells for viability, then at least 1000 non S-phase nuclei were scored for UDS from each cultre.

DETERMINATION OF CYTOTOXICITY
- Method: relative survival

OTHER EXAMINATIONS:
- Determination of polyploidy:
- Determination of endoreplication:
- Other:

OTHER:

Evaluation criteria:

A positive nucleus is one that has >4 net nuclear grain count. The criteria used for deermining a positive result is a statistically significant, reproducible and dose-related increase in the number of positive nuclei compared to the test solvent controls and the negative historical controls.

Statistics:

For statistical analysis, a two sample t-test is performed to determine significance.

Results and discussion

Test results

Species / strain:

hepatocytes: rat

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Remarks:

up to 10 μg/mL

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

In the evaluation of the preliminary cytotoxicity of test substance, there was a substantial reduction in cell viability at 20 μg/mL. Test substance at ≥ 40.0 μg/mL, was toxic to the cultures. There was evidence of insolubility in the cultures at test concentrations of ≥ 60.0 μg/mL.
For the UDS assay, at test concentrations at 1.7, 5.0 and 7.5 μg/mL, there was no increase in UDS compared to the concurrent solvent controls. Test substanse at 10.0 μg/mL produced insufficient viability (less than 25%) and therefore should not be considered in the UDS evaluation. A two sample t-test performed at concentrations of 1.7, 5.0, and 7.5 μg/mL, indicated there was no statistically significant difference (at the p≤5 level) in the number of positive cells between the solvent controls and the treated cultures. Test substance at ≥ 15.0 μg/mL was toxic to the cultures.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information):
negative

These studies indicate that the test substance does not induce UDS in primary cultures of rat hepatocytes at concentrations which produce marked reductions in cell viabilities.