[Study on the expression of vitamin D receptor in bone of immature rats of disuse osteoporosis].

OBJECTIVE

To study the expression of vitamin D receptor in bone of immobilized immature rat and explore the relation between disuse osteoporosis (DOP) and the expression of vitamin D receptor (VDR) in bone.

METHODS

Rats aging 4 weeks were immobilized by limb-tail fixation for 2 and 4 weeks respectively, and then the wet weight, gray weight, bone mineral density of femurs and tibiae were measured, the histopathological and histomorphological parameters also were detected, which were used to evaluate the effect of immobilization on bone content and bone structure of femurs and tibiae in growing rats. The VDR expression of femurs and tibiae in the growing rats was evaluated by immunohistochemistry and image analysis.

RESULTS

The wet weight, gray weight, and bone mineral density of immobilized limbs in the growing rats were all lower than those in age-matched control groups (P < 0.05). There were rare, small and broken bone trabeculae found in the histological films of proximal tibial metaphysis of immobilized limbs, with decreased trabecular area and perimeter (P < 0.05), comparing with the age-macthed control groups. Over-expression of VDR in cellular plasma and nuclear membranes of osteoblasts was also found in the proximal metaphysis of right hind limb in immobilized growing rats.

CONCLUSIONS

It is a definite method to establish animal model of DOP in young rats by leg-tail fixation; over-expression of Vitamin D receptors in growing bone of immobilized rat limbs means that the disorder of vittamin D endocrine system may be related to pathogenesis of DOP.