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Carcinogenesis Advance Access published online on October 4, 2007
Carcinogenesis, doi:10.1093/carcin/bgm217
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© The Author 2007. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Exposure of Fischer 344 rats to a weak power-frequency magnetic field facilitates mammary tumorigenesis in the DMBA model of breast cancer

Maren Fedrowitz and Wolfgang Löscher

Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, 30559 Hannover, Germany

Correspondence: Prof. W. Löscher, Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine, Bünteweg 17, D-30559 Hannover, Germany. Telephone: 49-511-953 8720; Fax: 49-511-953 8581; E-mail: wolfgang.loescher{at}tiho-hannover.de

The possibility that long term exposure to relatively weak power-frequency magnetic fields (MF) emanating from the generation, transmission, and use of electricity could increase the risk of breast cancer is a matter of ongoing debate. Laboratory studies using well-defined exposure conditions are useful to examine whether exposure to MF affects mammary tumorigenesis. Previous studies from different laboratories using the 7,12-dimethylbenz[a]anthracene (DMBA) model of breast cancer in female Sprague-Dawley (SD) rats have been inconclusive, which has been related to differences in MF sensitivity between SD substrains used in these studies. When we compared the effects of MF exposure on cell proliferation in the mammary gland of various outbred and inbred rat strains, Fischer 344 was the only inbred strain that exhibited a marked increase in cell proliferation. Based on these data, we suggested that MF exposure should significantly facilitate development and growth of mammary tumors in Fischer 344 rats, which was tested in the present study. Groups of 108 DMBA-treated rats were either MF-exposed (100 µTesla, 50-Hz) or sham-exposed for 26 weeks. MF exposure significantly facilitated mammary tumorigenesis. The incidence of rats with grossly recorded, histologically verified adenocarcinomas was increased by 45% (P = 0.0095). The most pronounced MF effect on tumor incidence was seen in the cranial inguinal complexes (L/R5). These data indicate that Fischer 344 rats are a suitable inbred strain to study the mechanisms underlying the effects of MF exposure on mammary tumorigenesis.

Key Words: Breast cancer • electromagnetic fields • melatonin • cell proliferation • rat strain differences

Received June 28, 2007; revised September 20, 2007; accepted September 23, 2007.


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