Efficacy of static magnetic field for locomotor activity of experimental osteopenia

Abstract

In order to examine the effectiveness of applying a static magnetic field (SMF) for increasing bone mineral density (BMD), we assessed the degree of osteopenia by dual-energy X-ray absorptiometry (DEXA), the metabolism measuring system, and histological examination of bone tissue in an ovariectomized (OVX) rat model. Thirty-six female Wistar rats (8 weeks old, 160-180 g) were divided into three groups. The rats in the OVX-M group were exposed to SMF for 12 weeks after ovariectomy. The ovariectomized rats in the OVX-D group were not exposed to SMF as a control. The rats in the normal group received neither ovariectomy nor exposure to SMF. Twelve-week exposure to SMF in the OVX-M group inhibited the reduction in BMD that was observed in the OVX-D group. Moreover, in the OVX rats, before exposure to SMF, there was no clear difference in the level of locomotor activity between the active and resting phases, and the pattern of locomotor activity was irregular. After exposure of OVX rats to SMF, the pattern of locomotor activity became diphasic with clear active and resting phases, as was observed in the normal group. In the OVX-M group, the continuity of the trabecular bone was maintained more favorably and bone mass was higher than the respective parameters in the OVX-D group. These results demonstrate that exposure to SMF increased the level of locomotor activity in OVX rats, thereby increasing BMD.

Figure 1.

Schematic diagram of magnet show its top plan view (A) and photograph (B). The mean magnetic force at the center of the cage was 30 mT (C).

Figure 2.

Locomotor activity system.

Figure 3.

Change in BW of OVX and normal rats before and after 12 weeks of exposure to SMF. OVX-D and normal groups were not exposed to SMF. Significant difference from normal group, mean ± SEM. **P < 0.01.

Figure 4.

Change in Serum T-Chol of OVX and normal rats before and after 12 weeks of exposure to SMF. OVX-D and normal groups were not exposed to SMF. Significant difference from normal group, mean ± SEM. **P < 0.01.

Figure 5.

Change in tail surface temperature of OVX and normal rats before and after 12 weeks of exposure to SMF. OVX-D and normal groups were not exposed to SMF. Significant difference from normal group, mean ± SEM. ***P < 0.001. Significant difference from OVX-M group, mean ± SEM. ^†††P < 0.001. Significantly different between before and after in OVX-M group, ^##P < 0.01.

Figure 6.

Change of locomotor activity of OVX-M, OVX-D and normal groups 24 hours of exposure to SMF. In OVX rats, before exposure to SMF, there was no clear difference between the active and resting phases, and the pattern of activity was irregular. After exposure, the pattern of activity became diphasic, with clear active and resting phases as was observed in the normal group.

Figure 7.

Change in locomotor activity of OVX and normal rats before and after 12 weeks of exposure to SMF. OVX-D and normal groups were not exposed to SMF. Significant difference from normal group, mean ± SEM. *P < 0.05, **P < 0.01. Significant difference from OVX-M group, mean ± SEM. ^†P < 0.05.