To study the effects of prenatal and postnatal long-term 24 hour exposure to 50 Hz extremely low frequency electric fields on growth, pubertal development, IGF-1 (insulin-like growth hormone-1) levels, and some endocrine glands related to puberty, such as hypothalamus, pituitary gland and gonads of female Wistar rats.
Pregnant rats were randomly distributed among three groups (n=8, each group): 1) the prenatal group was exposed to 24 hour during pregnancy and their subsequent randomly selected female pups were continuously exposed until puberty; 2) the postnatal group was unexposed during pregnancy, but randomly selected female pups from this group were exposed between delivery and puberty at the same doses and duration as the prenatal group; 3) sham-exposed group.
| Exposure | Parameters |
|---|---|
| Exposure 1: 50 Hz |
|
|
Exposure 2:
50 Hz
Exposure duration:
from birth until puberty (21 days)
|
|
| Exposure source |
|
|---|---|
| Setup | stainless steel plates placed upright on wooden stands 50 cm apart; 40 cm x 50 cm x 20 cm (wxlxh) plastic cages positioned between these plates |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | spatial average | calculated | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | from birth until puberty (21 days) |
| Exposure source |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | spatial average | calculated | - | - |
The mean birth weight and weight gain of the pups was significantly reduced in the prenatal group (1) compared to postnatal (2) and sham-exposed (3) groups. No difference was found in the body weights at puberty of the three groups. The mean age at vaginal opening and estrous was significantly higher in the prenatal group (1) compared to postnatal (2) and sham-exposed (3) groups. IGF-1 levels were significantly reduced in the prenatal exposure group compared with the other two groups.
There was no difference in birth weight, weight gain, the mean age at vaginal opening and estrous and IGF-1 levels between postnatal and sham-exposed groups.
There was also no difference in the levels of follicle stimulating hormone, luteinizing hormone and estradiol at puberty among the three groups. Histological examination revealed tissue damage in hypothalamus, pituitary gland and ovaries in both exposed groups (prenatal and postnatal).
The authors conclude, that early beginning of prenatal exposure to 24 hours 50 Hz electric field at 10 kV/m until puberty (without magnetic field) resulted in growth restriction, delayed puberty and reduced IGF-1 levels in female Wistar rats. Postnatal exposure to electric fields at similar doses and duration seemed to be less harmful.
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