Mammary tumors were induced by the use of the chemical carcinogen DMBA. The first DMBA application (5mg/rat) at the onset of exposure was followed by three more applications at weekly intervals up to a total of 20 mg DMBA/rat.
A total of 216 animals were used in this study, divided into four groups. Group A) 99 animals, DMBA treated, MF exposed. Group B) 99 animals DMBA treated, sham-exposed. Group C) 9 animals, non DMBA treated, MF exposed. Group D) 9 animals, non DMBA treated, sham-exposed.
|magnetic flux density||50 µT||-||measured||-||-|
8 weeks after DMBA application, significantly more tumors were found in the MF-exposed group than in sham-exposed animals. At time of autopsy, significantly more MF-exposed DMBA-treated animals exhibited macroscopically visible mammary tumors than DMBA-treated controls.
Proliferation of spleenic T lymphocytes was determined at the end of exposure time and revealed a significant suppression in MF exposed non DMBA treated animals compared with MF sham-exposed non DMBA treated rats.
No signifficant difference was seen in nocturnal melatonin levels of DMBA-treated MF exposed and sham-exposed animals. (determination after 9 and 12 weeks after onset of exposure.)
Other findings: No behavioural differences were observed between exposed and sham-exposed animals. Furthermore, no significant differences were found for body weight, spleen, and liver weight were among the four groups.
The results of this study indicates that long-term 50 µT MF exposure of DMBA-treated female rats significantly enhances mammary tumor development and growth.