The mechanism of osteoporosis induced by prednisone

Aim To investigate the mechanism of osteoporosis induced by long-term administration of prednisone.Methods Forty SD rats were randomly divided into 4 groups with 10 rats per group.Group 1 was treated orally with vehicle as control, other groups were oral gavages prednisone (1,3 mg·kg-1or 9 mg·kg-1), once a day for 12 weeks.At the experimental endpoint, the undecalcified longitudinal proximal tibia was cut for osteoclasts analysis and for the cancellous bone histomorphometric and fluorochrome labeling analysis,the desiccant left ulnar was used for testing the content of Ca2+ and hydroxyproline.Length and width of the thighbone were tested to observe the instance of bone growth.Results Compared with control group, the %Tb.Ar reduced by 46.38%,41.40% and 9.75% respectively in group PrH、PrM and PrL.Tb.N reduced by 64.04%,52.74% and 2.74%;Tb. Th reduced by 29.81%,21.96% and 6.05% respectively.But Oc.N/BV increased by 274.0%,236.08% and 77.85%;%Oc.pm increased by 161.17%,190.95% and 68.38%. Contents of bone hydroxyproline and Ca2+/P3+ decreased remarkably in group PrH and PrM,and the fat was showed markedly in the marrow of the prednisone group.Conclusions Bone loss occured in four-month-old male Sprague-Dawley rats after prednisone-treated for 12 weeks in the dose of 3 mg·kg-1 or 9 mg·kg-1. The mechanism may be related to the fact that prednisone can stimulate osteoclast,inhibite osteoblast, and increase the fat cell in bone marrow.