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

Abstract

An animal model for large granular lymphocytic (LGL) leukemia in male Fischer 344 rats was utilized to determine whether magnetic field exposure can be shown to influence the progression of leukemia. We previously reported that exposure to continuous 60 Hz, 1 mT magnetic fields did not significantly alter the clinical progression of LGL leukemia in young male rats following injection of spleen cells from donor leukemic rats. Results presented here extend those studies with the following objectives: (a) to replicate the previous study of continuous 60 Hz magnetic field exposures, but using fewer LGL cells in the inoculum, and (b) to determine if intermittent 60 Hz magnetic fields can alter the clinical progression of leukemia. Rats were randomly 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 microT), 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 LGL leukemic spleen cells at the beginning of the study. The fields were activated 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 after transplantation of the leukemia cells. Hematological evaluations were performed at 6, 8, 10, 12, 14, and 16 weeks of exposure. Peripheral blood hemoglobin concentration, red blood cells, and packed cell volume declined, and total white blood cells and LGL cells increased dramatically in all treatment groups after onset of leukemia. Although the positive control group showed different body weight curves and developed signs of leukemia earlier than other groups, differences were not detected between exposure groups and ambient controls. Furthermore, there were no overall effects of magnetic fields on splenomegaly or survival in exposed animals. In addition, no significant and/or consistent differences were detected in hematological parameters between the magnetic field exposed and the ambient control groups.

Magnetic Fields and Cancer: Epidemiology, Cellular Biology, and Theranostics

“…No overall effects of 60 Hz and 1 mT MF on splenomegaly or survival were found in the exposed Fischer/344 rats. In addition, no significant and/or consistent differences were detected in the hematological parameters between the exposed and control rats [242]. MF exposure for 14 weeks to 6.45 µT did not appear to be a strong co-tumorigenic agent in Sprague-Dawley female rats mammary, lung, and skin models [243].…”

The Risk of Lymphoma in AKR/J Mice does not Rise with Chronic Exposure to 50 Hz Magnetic Fields (1 μT and 100 μT)

“…Only in male rats was the incidence of thyroid gland C-cell neoplasm increased when they were exposed to 2 or 200 T (28), whereas in the study of McCormick et al (39) lymphoma development in female mice exposed to 1 mT was even decreased. Fischer 344 rats were also used to study whether magnetic-field exposure (60 Hz) can influence the progression of leukemia after intraperitoneal injection with leukemic spleen cells (40). No influence of the exposure could be detected on body weight, survival, splenomegaly or leukemia incidence rate.…”

Assessing the Potential Carcinogenic Activity of Magnetic Fields Using Animal Models

“…In our previous review (1) we discussed experiments of Dieter and colleagues (100) and suggested that their report of enhancement effects may not be definitive. More (79)(80)(81)(82)101) appear to be well done, the significance of the results with respect to whether MFs have any leukemogenic potential is uncertain. Below, we review the experiments conducted by this group.…”