Studying effects of 50 Hz sinusoidal electromagnetic fields (SEMFs) with different intensities on peak bone mass (PBM) of rats may provide a theoretical basis for application of electromagnetic clinical field. 30 female SD rats, 6 weeks of age, were randomly divided into three groups: the control group, 0.1 mT electromagnetic field group (EMFs) and 0.6 mT EMFs. The EMFs groups were treated for 3 h/day. After 8 weeks, we examined their bone mineral densities (BMD), measured their bone biomechanical properties, and made serum levels of osteocalcin (OC), tartrate-resistant acid phosphatase 5b (TRACP 5b), and histomorphometry. It was found that the BMD (P < 0.01), maximum mechanical load (P < 0.01) in the 0.1 mT group were significantly higher than those in the control group, and Yield strength (P < 0.05), the analyses of serum bone turnover markers and histomorphometric parameters were better than those in the control group (P < 0.05). However, the 0.6 mT group did not have significantly difference comparing with that in the control group. This study proved that 50 Hz 0.1 mT SEMFs can increased BMD, bone strength, and bone tissue microstructure. Therefore, 50 Hz 0.1 mT SEMFs can improve peak bone mass of rats.
The present research is to investigate the time effect of sinusoidal electromagnetic fields (SEMFs) at different exposure time on the biomechanical properties in rats, and to find a best time for improving biomechanical properties. Forty female SD rats were randomly divided into five groups, i.e. control group, 45 min SEMFs group, 90 min SEMFs group, 180 min SEMFs group, and 270 min SEMFs group. In addition to the control group, other groups were exposed to 50 Hz and 0.1 mT magnetic field every day for the corresponding time periods. After eight weeks, bone mineral density (BMD), bone biomechanics, bone tissue morphology, micro-CT and pathological examination were performed. The results showed that there was no abnormal pathological finding in the experimental groups. In the 90 min SEMFs group, BMD, femur maximum load, elastic modulus, yield strength, trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular area (Tb.Ar) percentage were all significantly higher than those in the control group (P＜0.01), and trabecular separation (Tb.Sp) was significantly lower than that of the control group (P＜0.01). However, for other experimental groups, some indices showed statistical significance compared to the control group (P＜0.05), but some did not (P>0.05). This study showed that under 50 Hz and 0.1 mT SEMFs, 90 min is the best time that can effectively increase bone mineral density, improve the bone tissue microstructure organization and the biomechanical properties.