Estimation of the effects of prednisolone on bone metabolism in rats by biochemical markers

The effects of prednisolone treatment on bone turnover in rats were studied by biochemical markers. Female Wistar rats were randomized into three groups: (1) control; (2) prednisolone 25 mg/kg body weight (BW) (lower dose), twice a week subcutaneously; and (3) prednisolone 50mg/kg BW (higher dose). Serum calcium, phosphorus, alkaline phosphatase (Alp), and urinary pyridinoline (Pyr) and deoxypyridinoline (Dpyr) were measured once a week for 4 weeks. Bone mineral density (BMD) of excised femur, tibia, and lumbar vertebrae were measured by dual energy X-ray absorptiometry (DXA). Dry and ash weights of excised femur were measured by conventional methods, and the content of pyridinium cross-links in tibias was measured. Higher prednisolone treatment produced a significant increase of urinary Pyr and Dpyr at weeks 3 and 4. Although serum osteocalcin was not found to be reduced in prednisolone treatment except at week 4 in the higher prednisolone treatment group, BMD and dry and ash weights of excised bones was reduced by prednisolone administration. Further, the content of Pyr and Dpyr in bone was reduced by prednisolone administration. Our findings confirm that prednisolone induced osteoporosis in rats, mainly because of the increase of bone resorption activity.