Objective   To investigate the effects of pulsed electromagnetic fields (PEMF) on the bone mineral density (BMD) and serum level of transforming growth factor-beta 1 (TGF-β

1

) in the disuse osteoporosis (DOP) rats.    Methods   Eighty 4-month-old female

SD rats were randomly divided into 4 matched groups according to their weight: control group (INT group)

DOP group

calcitonin group (CT group) and PEMF group. Rats in INT group were raised with the average amount of food consumed by the DOP rats. Right hindlimbs of rats in DOP

CT and PEMF groups were immobilized by tibia-tail fixation to establish DOP model as Zarzhevsky described . Rats in CT group were injected with calcitonin (2 IU/kg

i.p

once a day)

and rats in group PEMF were irradiated with PEMF (8 Gs

15 Hz

a pulse time of 8 ms) immediately after operation. The rats (5 animals per time of each group) were killed at 1

2

4 and 8 weeks after operation and their right hindlimbs were resected. The BMD and serum TGF-β

1

concentration were measured with a dual energy X-ray bone densitometer and ELISA respectively.    Results   Significant difference was observed in the femur proximal BMD between rats with right hindlimb immobilization (DOP group) and INT group 2 weeks later (P0.01). Compared with CT group and DOP group

the BMD and serum TGF-β

1

concentration in PEMF group were increased significantly at 8 weeks after operation (P0.05).    Conclusion   PEMF and calcitonin can prevent BMD decline in DOP rats

but PEMF is more effective at later stage. There is a diphase change of TGF-β

1

in DOP rats

PEMF may affect bone remodeling by promoting TGF-β

1

secretion.