EXPOSURE TO 60 HZ MAGNETIC-FIELDS AND RISK OF LYMPHOMA IN PIM TRANSGENIC AND TSG-P53 (P53 KNOCKOUT) MICE

The results of a number of epidemiology studies suggest that exposure to power frequency (50 and 60 Hz) magnetic fields may be a risk factor for hematopoietic neoplasia, To generate experimental data to test th is hypothesis, the influence of magnetic field exposure on lymphoma in duction was determined in two strains of mice that are genetically pre disposed to the disease, PIM mice, which carry the pim-1 oncogene, are highly sensitive to lymphoma induction by N-ethyl-N-nitrosourea (ENU) ; ENU-treated PIM mice were studied as a 'high incidence' lymphoma mod el, TSG-p53 (p53 knockout) mice, in which the p53 tumor suppressor gen e has been deleted from the germ line, develop lymphoma as an age-rela ted change; hemizygous TSG-p53 mice were studied as a 'low incidence' lymphoma model, Beginning 1 day after a single i.p. injection of 25 mg ENU/kg body wt, groups of 30 PIM mice/sex were exposed for 18.5 h/day to pure, linearly polarized, transient-free 60 Hz magnetic fields at field strengths of 0 (sham control), 0.02, 2.0 or 10.0 Gauss (G), An a dditional group of 30 PIM mice/sex was exposed intermittently (1 h on, 1 h off) to 10.0 G fields, Groups of 30 TSG-p53 mice/sex were exposed continuously to magnetic field strengths of 0 (sham control) or 10.0 G; TSG-p53 mice received no ENU, Studies were terminated after 23 week s of magnetic held exposure. Lymphoma incidence in male PIM mice expos ed continuously to 10.0 G magnetic fields was significantly reduced fr om that seen in sex-matched sham controls; survival, lymphoma incidenc e and lymphoma latency in other groups of PIM mice did not differ from sham controls, Survival and lymphoma incidence in all groups of TSG-p 53 mice was 7% or less, regardless of magnetic field exposure regimen, These data do not support the hypothesis that exposure to magnetic fi elds is a significant risk factor for lymphoid neoplasia in mice with a genetic predisposition to the disease.