[Effect of pulsed electromagnetic fields of different treatment time on bone mineral density of femur in ovariectomized rats].

OBJECTIVE: To observe the effect of pulsed electromagnetic fields (PEMFs) of different treatment time on bone mineral density of femur in ovariectomized rats, so as to find out the treatment time for the best therapeutic efficacy. METHODS: Fifty female SD rats were randomly divided into 5 groups: sham-ovariectomized (SHAM) group (no PEMFs treatment), ovariectomy (OVX) control group (no PEMFs treatment), OVX I, II and III groups (PEMFs treatment at 8 Hz frequency with 3.8 x 10(-10) A/m intensity 20, 40, and 60 minutes daily for 30 days, respectively). All rats were given bilateral ovariectomy except those in the SHAM control group. Bone mineral density (BMD) of femur was assessed at 30 days after PEMFs treatment. RESULTS: In OVX control group, hypotrichosis, hypoactivity and listlessness were observed after operation; and in SHAM group, OVX I group, OVX II group and OVX III group, pilus, psyche and activity were normal. The BMD values were (0.226 +/- 0.011), (0.210 +/- 0.011), (0.231 +/- 0.013), (0.231 +/- 0.017) and (0.229 +/- 0.013) g/cm2 in SHAM group, OVX control group, OVX I group, OVX II group and OVX III group respectively, showing significant differences between OVX control group and other groups (P < 0.05), but showing no significant differences between other 4 groups (P > 0.05). CONCLUSION: PEMFs of the three different treatment times can maintain the BMD in ovariectomized rats. It shows that PEMFs have the same effect of maintaining BMD with increasing of treatment time at the range of 20-60 minutes in ovariectomized rats.