Studies of bone tissue in rats treated by prednisolone and 1,25-(OH)2D3.

Adult male rats were treated for six weeks by prednisolone and/or 1,25-(OH)2D3 and given a diet containing either 0.5% calcium or 0.01% Ca and 0.6% phosphorus. Both prednisolone administration and a low-Ca diet were associated with a lower bone mass than that observed in control rats given a 0.5% Ca diet. The percentage of osteoid surface was decreased in rats given prednisolone; these rats also had a lower osteoclast number. The results were consistent with a lower bone turnover during prednisolone treatment. Administration of 1,25-(OH)2D3, resulting in a slightly higher mean level of 1,25-(OH)2D3 in serum, had a positive effect on bone mass, which may be related to increased osteoblastic activity; no increase in the osteoclast number occurred.