Large granular lymphocytic (LGL) leukemia in rats exposed to intermittent 60 Hz magnetic fields

An animal model for large granular lymphocytic (LGL) leukemia in male Fisch er 344 rats was utilized to determine whether magnetic field exposure can b e shown to influence the progression of leukemia. We previously reported th at exposure to continuous 60 Hz, 1 mT magnetic fields did not significantly alter the clinical progression of LGL leukemia in young male rats followin g injection of spleen cells from donor leukemic rats. Results presented her e extend those studies with the following objectives: (a) to replicate the previous study of continuous 60 Hz magnetic field exposures, but using fewe r LGL cells in the inoculum, and (b) to determine if intermittent 60 Hz mag netic fields can alter the clinical progression of leukemia. Rats were rand omly assigned to four treatment groups (18/group) as follows: (1) 1 mT (10 G) continuous field, (2) 1 mT intermittent field (off/on at 3 min intervals ), (3) ambient controls (< 0.1 <mu>T), and (4) positive control (5 Gy whole body irradiation from cobalt-60 four days prior to initiation of exposure) . All rats were injected intraperitoneally with 2.2 x 10(6) fresh, viable L GL leukemic spleen cells at the beginning of the study. The fields were act ivated for 20 h per day, 7 days per week, and all exposure conditions were superimposed over the natural ambient magnetic field. The rats were weighed and palpated for splenomegaly weekly. Splenomegaly developed 9-11 weeks af ter transplantation of the leukemia cells. Hematological evaluations were p erformed at 6, 8, 10, 12, 14, and 16 weeks of exposure. Peripheral blood he moglobin concentration, red blood cells, and packed cell volume declined, a nd total white blood cells and LGL cells increased dramatically in all trea tment groups after onset of leukemia. Although the positive control group s howed different body weight curves and developed signs of leukemia earlier than other groups, differences were not detected between exposure groups an d ambient controls. Furthermore, there were no overall effects of magnetic fields on splenomegaly or survival in exposed animals. In addition, no sign ificant and/or consistent differences were detected in hematological parame ters between the magnetic field exposed and the ambient control groups. (C) 2001 Wiley-Liss, Inc.