It should be investigated if an in utero exposure of mice to a 50 Hz magnetic field can induce double-strand breaks or influence the DNA repair of X-radiation-induced double-strand breaks (magnetic field exposure 3 hours prior to and up to 9 hours after X-radiation).
48 pregnant mice were divided into 6 groups: 1) magnetic field sham exposure for 9 hours (n=4), 2) exposure to the magnetic field for 9 hours (n=4), 3) X-radiation sham exposure for 10 minutes (examination 1 and 6 hours afterwards) (n=8), 4) X-radiation (100 mGy) for 20 minutes (examination 1 h, 3 h, 6 h and 11 hours afterwards) (n=8), 5) magnetic field sham exposure for 3 hours, X-radiation for 20 minutes and afterwards further magnetic field sham exposure (examination 1 h and 6 hours after X-radiation) (n=8), 6) exposure to the magnetic field for 3 hours, X-radiation for 20 minutes, afterwards further exposure to the magnetic field for up to 9 hours (examination 1 h, 3 h, 6 h and 11 hours after X-radiation) (n=16).
The magnetic field exposure of the mothers started when the embryos were 13.5 days old. For each measurement time point in each group, 2 brain sections/embryo of each of 3 embryos/mother of each of 4 mothers (i.e. n=24 for each measurement point) were investigated, except for group 4) with only 2 mothers for each measurement point (i.e. n=12 for each measurement point). The experiment was repeated once.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 3 hours prior to and up to 9 hours after X-radiation
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 3 hours prior to and up to 9 hours after X-radiation |
| Exposure source | |
|---|---|
| Chamber | non-metallic cage |
| Setup | up to four pregnant mice were housed in a non-metallic cage in the center of a pair of Helmholtz coils (vertical field; inner radius of coils = 25.5 cm); average noise levels were 63 dB(A) |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 300 µT | - | measured | - | ± 5% |
All groups with X-radiation exposure (4-6) showed significantly higher numbers of double-strand breaks compared to the X-radiation-sham exposed group (3).
There were no significant differences between group 1 and 2 (magnetic field sham exposure and exposure) and between group 5 and 6 (magnetic field sham exposure and exposure + X-radiation). However, within the groups, there were significant differences between the mothers, but this had no impact on the significance of the other results.
The authors conclude that there is no evidence that an in utero exposure of mice to a 50 Hz magnetic field could induce double-strand breaks or influence the DNA repair of X-radiation-induced double-strand breaks.
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