To investigate whether magnetic field exposure is capable to influence the initiation event or the progress of tumor development in a rat liver model.
Male rats were subjected to a 70% partial hepatectomy and magnetic field exposure (0.5 µT or 0.5 mT) was started. 24 h thereafter 30 mg/kg diethylnitrosamine was injected intraperitoneal as a tumor initiator. One week later phenobarbital was given to promote growth of altered liver cells. Magnetic field exposure was applied for 13 weeks. Rats were administered to a special diet, which did not induce the enzyme gamma-glutamyl transpeptidase.
Liver tissue slices were examined histopathologically for the presents of the enzymes gamma-glutamyl transpeptidase and glutathione S-transferase serving as markers for altered cell growth.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
repeated daily exposure, 19 h/day on week days and 21 h/day on weekends and holidays, for 13 weeks
|
|
|
Exposure 2:
50 Hz
Exposure duration:
repeated daily exposure, 19 h/day on week days and 21 h/day on weekends and holidays, for 13 weeks
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | repeated daily exposure, 19 h/day on week days and 21 h/day on weekends and holidays, for 13 weeks |
| Additional info | Reference article regarding the quadrupole coil design: Harvey SM (1987): "Magnetic-Field Exposure Apparatus for Small Animal Studies: Phase 2." Ontario Hydro Research Division, Report No 87-118K. |
| Exposure source | |
|---|---|
| Chamber | Polycarbonate plastic cages with polyacrylamide cage tops |
| Additional info | Copper bars mounted on a wooden frame hence making a floor or a level. On each level, five cages were placed on PV cell boards which were held by metal consoles from the wall thus avoiding contact between the copper bars and the cages. Twice a week the position of the cages were changed in the rack. An extra board was placed on the top of the whole exposure apparatus to make similar light conditions on each level. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 500 nT | unspecified | measured | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | repeated daily exposure, 19 h/day on week days and 21 h/day on weekends and holidays, for 13 weeks |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 500 µT | unspecified | measured | - | - |
Animals exposed to the magnetic fields exhibited a greater liver weight than unexposed controls. Partial hepatectomy followed by diethylnitrosamine-treatment produces pre-neoplastic liver lesions indicated by the expression of the above mentioned enzymes. In the magnetic field-exposed groups these lesions were slightly inhibited.
The results suggest an interaction of magnetic fields with the process of chemically induced carcinogenesis.
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