| Abstract: | We established a useful assay system for evaluating osteoclast-mediated bone resorption based on the use of unfractionated bone cells obtained from 10- to 11-day-old mice. When cells from 10 to 11 mice were treated for 7 days with rat parathyroid hormone (rPTH, 10−8 M), a total of 4 to 5 × 107 cells could be obtained from the culture by treatment with 0.05% trypsin and 0.02% EDTA in PBS. These harvested cells contained about 20% tartrate-resistant acid phosphatase (TRAP)-positive mononuclear cells. When the harvested cells were cultured on dentine slices without rPTH, after 1 day, they formed TRAP-positive multinucleate cells that were active in bone rsorption. Eel calcitonin (eCT) decreased the number of pits in a dose-dependent manner, and its half maximal inhibition dose (ID50) was 1.08 × 10−11 M.Even after having been frozen in liquid nitrogen for 5 months, upon thawing, these cells were capable of forming pits; and this pit formation was inhibited by eCT. Since no appropriate osteoclaslic cell line for evaluating bone resorption is available at present, this system can provide a useful, practical means for assaying osteoclastic bone-resorbing activity. |
