To study the functionality and expression of alpha-amylase in the breast tissue of Fischer 344 rats as well as serum enzyme activity after magnetic field exposure. For some experiments, Lewis rats were included and compared to Fischer 344 rats.
Fischer 344 rats and Lewis rats are two strains with distinct stress sensitivity and magnetic field susceptibility. Fischer 344 rats show higher corticosterone and ACTH levels after stress than Lewis rats. In a previous study (Fedrowitz and Löscher 2012), a gene expression analysis in the mammary gland revealed a marked alteration of alpha-amylase in magnetic field exposed Fischer 344 rats but not in Lewis rats. These data prompted the authors to investigate the magnetic field effects on alpha-amylase in more detail.
For comparison with the magnetic field effects on alpha-amylase activity, diethylstilbestrol (DES; an estrogen-like acting substance, which stimulates proliferation and differentiation in the mammary gland tissue) was applied to Fischer 344 rats to investigate alpha-amylase in breast tissue under estrogenic influence.
158 female Fischer 344 rats and 36 Lewis rats at an age of 42-45 days were used in 10 independent experiments over a time period of four years.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 1 day, 7, 14 and 28 days (24 h/day; except time for weighing and cage cleaning)
|
|
|
Exposure 2:
50 Hz
Exposure duration:
continuous for 14 days (24 h/day; except time for weighing and cage cleaning)
Lewis rats
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 1 day, 7, 14 and 28 days (24 h/day; except time for weighing and cage cleaning) |
| Additional info | Fischer 344 rats |
| Exposure source |
|
|---|---|
| Setup | rats were exposed in groups of 5-10 animals; controlled conditions of temperature (23-24°C), humidity (about 50%) and light (12 h dark/light cycle) and free access to food and water |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 100 µT | - | measured | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 14 days (24 h/day; except time for weighing and cage cleaning) |
| Additional info | Lewis rats |
| Exposure source |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 100 µT | - | measured | - | - |
In the first set of experiments, alpha-amylase enzyme activity was significantly enhanced in the Fischer 344 and Lewis rats cranial mammary gland complexes after two weeks of magnetic field exposure as well as after 28 days in Fischer 344 rats without any alterations in the caudal mammary gland complexes. In a second set of experiments, a moderate, but statistically significant increase in enzyme activity was found in the caudal mammary gland complexes in Fischer 344 rats after 14 days of exposure, but not in Lewis rats.
In one of the two sets of experiments, protein expression of alpha-amylase was significantly elevated in caudal mammary gland complexes after magnetic field exposure for 14 days, but not in the cranial mammary gland complexes.
There were no significant differences in the alpha-amylase enzyme activity in serum between sham exposed and magnetic field exposed rats after 1, 7 and 14 days.
Although alpha-amylase represents a difficult parameter in animal studies because of its stress sensitivity, it should be considered for investigations of magnetic field effects in humans as a marker for stress and as a target to examine possible magnetic field mechanisms.
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