Identification of rat osteoclasts in bone smears with quantification of acid phosphatase activity in vitamin D...

Vitamin D deficiency may depress bone formation but its effect on bone resorption is not well defined. As an index of bone resorption, the activity of acid phosphatase, a lysosomal enzyme found in osteoclasts, was quantitated in situ from a bone tissue smear preparation. Activity of the enzyme, measured by integrative microdensitometry increased linearly from 25 to 60 min. The distribution of activity in osteoclasts quantitated appeared to follow a normal distribution with a median value of 0.19 integrated optical density units. Animals treated with vitamin D or 1,25 dihydroxycholecalciferol had significantly increased activity of acid phosphatase in osteoclasts compared to animals which were vitamin D deficient. The increase of acid phosphatase activity averaged 63%. Vitamin D or its metabolites may have a permissive effect on the action of parathyroid hormone or act directly to increase bone resorption.