EFFECT OF LOW-FREQUENCY LOW-ENERGY PULSING ELECTROMAGNETIC-FIELDS ON MICE INJECTED WITH CYCLOPHOSPHAMIDE

C3H mice have been used to investigate the effect of a combination of cyclophosphamide (CY) and electromagnetic fields (PEMF). Mice were injected i.p. with a single dose of 200 mg/kg body weight of CY and then exposed to PEMF 24 h per day. In an initial series of experiments immediately after CY injection mice were exposed to PEMF until sacrifice. WBC counts in the peripheral blood demonstrated a quicker decline in WBC at days 1 and 2 in mice exposed to PEMF. Groups of mice were sacrificed at days 1, 4, 6, 8, and 10 after CY injection. In mice exposed to PEMF the spleen weight was less than in controls at days 6, 8, and 10. Autoradiographic studies demonstrated that the labeling index of bone marrow smears did not significantly differ between controls and experimental mice exposed to PEMF, whereas the spleen labeling index proved to be higher among control mice versus mice exposed to PEMF at day 6, and higher among mice exposed to PEMF versus controls at day 8. In a second series of experiments mice were exposed to PEMF only over the 24 h following CY injection. We found that the spleens of mice exposed to PEMF weighed less than those of controls at days 6 and 8. The labeling index of bone marrow did evidence a slight decrease among mice exposed to PEMF at days 8 and 10 after CY injection versus control mice. The spleen labeling index proved to be lower in experimental mice exposed to PEMF than in controls at days 4, 6, and 8. Mice were then injected with CY, half were exposed to PEMF, and 24 h later bone marrow was recovered from both groups of animals. The same number of bone marrow cells was injected via the tail vein into recipient mice irradiated to 8.5 Gy. The grafting efficiency of the bone marrow was evaluated by examining the number of spleen colonies and the spleen and bone marrow labeling indices at day 8; all parameters proved to be significantly lower among mice grafted with the bone marrow of mice injected with CY and exposed to PEMF than among controls injected with CY only. Finally, we found that the effect of PEMF is evident only if mice are exposed during the 24 h following CY injection. The data reported here indicates that PEMF exposure after CY injection increases the damage induced in mice by CY.