A TEST OF LYMPHOMA INDUCTION BY LONG-TERM EXPOSURE OF E-MU-PIM1 TRANSGENIC MICE TO 50 HZ MAGNETIC-FIELDS

E mu-Pim1 transgenic mice expressing a dysregulated Pim1 oncogene in t heir lymphoid cells were used to test whether exposure to 50 Hz magnet ic fields can increase the frequency of malignant lymphoma in mice of a strain predisposed to develop such tumors spontaneously at low incid ence. Specific-pathogen-free female mice were allocated randomly into groups of approximately 100 at 6-8 weeks of age and then exposed for 2 0 h/day for up to 18 months to sinusoidal magnetic fields of 0, 1, 100 or 1000 mu T, or 1000 mu T pulsed 15 min on and 15 min off. Additiona l E mu-Pim1 mice were injected with ethylnitrosourea (50 mg/kg body we ight) as positive controls for enhanced lymphomagenesis; these yielded a cumulative incidence of lymphoma of 60% in 9 months. A lethal, tran sgene-dependent renal glomerular disease occurred at a frequency that varied from 9% to 19% among the groups, but the increase was statistic ally significant only at the 1000-mu T exposure. Lymphoblastic and non -lymphoblastic (predominantly follicular) lymphomas were seen in 26 to 35% of the exposed mice, but at no significantly higher incidence tha n the 29% found in the sham-exposed mice. Hence we conclude that the l ymphoma-prone mice did not reveal any tumorigenic effect of long-term exposure to 50 Hz magnetic fields. (C) 1998 by Radiation Research Soci ety.