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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian cell study: DNA damage and/or repair
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2001

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Male mice were exposed via inhalation to 0.0068 ug/cc lead acetate for 60 minutes and liver, lung, and kidney cells were collected for an acellular DNA assay using lead acetate concentrations of 0.01, 0.1, and 1 uM.
GLP compliance:
not specified
Type of assay:
mammalian comet assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
Lead acetate was obtained from Merck (Germany)

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Biomedical Research Institute Vivarium, UNAM, Mexico
- Age at study initiation: 45-63 days
- Weight at study initiation: 30-35 g
- Housing: plastic cages
- Diet: ad libitum, purine rat chow
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 15-19
- Humidity (%): 45-55
- Photoperiod : 12 hour light/12 hours dark

Administration / exposure

Route of administration:
inhalation: aerosol
Vehicle:
Deionized water
Details on exposure:
Inhalation exposure was performed in an acrylic box connected to an ultra-nebulizer with a flux of 10 L/min. Animals were placed in the box with 0.0068 ug/cc lead acetate for 60 minutes.
Duration of treatment / exposure:
60 minutes
Frequency of treatment:
Once
Doses / concentrations
Remarks:
0.0068 ug/cc
Basis: nominal conc.
No. of animals per sex per dose:
3 per group
Control animals:
yes, concurrent vehicle
Positive control(s):
None

Examinations

Tissues and cell types examined:
Liver, kidney, and lung tissues were removed and cells were isolated for in vitro studies.
Details of tissue and slide preparation:
Cell suspensions were mixed with LMPA and loaded onto microscope slides prelayered with agarose. Slides were immersed in a lysis solution, then an acellular assay for DNA migration was performed with 10 nM to 1 uM lead acetate. For this assay, slides were immersed in 50 ml PBS with lead acetate for 10 minutes, then electrophoresed and stained with ethidium bromide. DNA migration was evaluated by visualization with a fluorescence microscope.
Evaluation criteria:
DNA migration was evaluated on 100 cells/tissue/animal.
Statistics:
Mann-Whitney U-test for statistical differences between treatments in the acellular assay. ANOVA t-test for differences of free radicals and lipid peroxidation.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
not examined

Any other information on results incl. tables

DNA damage was induced by lead in all tissues examined, but a dose-response relationship was not observed. Lead in combination with cadmium (0.1 uM) showed a synergistic effect in lung and kidney, but not liver, cells. In the presence of proteinase K, lead did not induce DNA damage in the acellular assay. Because of the inconsistent results, additional genomic DNA and the plasmid pUSE amp+ were examined with lead exposure and no DNA damage was observed. Lead induced the production of free radicals and lipid peroxidation in lung and liver cells.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
The authors suggested that lead does not directly interact with DNA, rather it may affect DNA through indirect mechanisms, such as oxidative stress or interaction with DNA-associated proteins.
Executive summary:

Male mice were exposed via inhalation to 0.0068 ug/cc lead acetate for 60 minutes and liver, lung, and kidney cells were collected for an acellular DNA assay using lead acetate concentrations of 0.01, 0.1, and 1 uM. DNA damage was induced by lead in all tissues examined, but a dose-response relationship was not observed. Lead in combination with cadmium (0.1 uM) showed a synergistic effect in lung and kidney, but not liver, cells. In the presence of proteinase K, lead did not induce DNA damage in the acellular assay. Because of the inconsistent results, additional genomic DNA and the plasmid pUSE amp+ were examined with lead exposure and no DNA damage was observed. Lead induced the production of free radicals and lipid peroxidation in lung and liver cells. The authors suggested that lead does not directly interact with DNA, rather it may affect DNA through indirect mechanisms, such as oxidative stress or interaction with DNA-associated proteins.