EXTRACELLULAR PROTEIN SECRETION OF CULTURED NORMAL AND PAGETIC OSTEOBLASTS

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) has been used to map the extracellular secretory activity of normal osteoblast s. The proteins osteonectin, bone sialoprotein, and both the C-telopep tide of collagen I together with collagen I have now been positionally identified. In addition the secretory differences which exist between normal and Pagetic osteoblasts have been mapped with the Pagetic oste oblasts shown to consistently secrete an altered 30 kDa C-telopeptide of collagen type I. The use of the diphosphonate Pamidronate in the tr eatment of Paget's disease of bone has beneficial effects with suppres sion of the bone isoenzyme marker alkaline phosphatase. It has been re ported that diphosphonates directly inhibit human osteoblast secretory function as well as osteoclast metabolism. The effects of Pamidronate on the secretory activity of normal and Pagetic osteoblast cultures w as also investigated. The extracellular protein secretion of normal an d Pagetic osteoblasts was not affected by Pamidronate treatment as ass essed by 2-D PAGE. This technique allows a comprehensive multiparamete r assessment of extracellular secretory activity in normal and disease d states. The findings show that the Pagetic osteoblasts cultured in v itro are functionally abnormal and they support the hypothesis that th e underlying problem in Paget's disease is characterised by disorder o f osteoblast and osteoclast interactions.