| Research Abstract |
1. Nine clonal lines were generated (C5.4D, C5.4E, C5.4G, C5.6A, C5.8B, C5.8G, C5.10C, C5.10H) from rat osteosarcoma cells (MSK) by limited dilution methods.
2. By light microscopy, clonal lines appeared fusiform fibroblast-like cells or small polygonal epitheial cell-like cells in different proportions. A certain pleomophism was presented in each clonal lines.
3. The alkaline phosphatatase activities of the clonal cell lines ranged from 16.1% to 308.1% of MSK cell. The enzyme activities was not correlated with hydroxyprline production and PTH responsiveness. In transplantation into isogenic rats, hihg ALPase activity group (C5.4D, C5.4E, C5.4G, C5.8B, C5.8G, C5.10C, C5.10H) metastasized to the lung frequently, whereas the low activity group (C5 6A, C5.8H) showed no pulmonary metastases.
4. The hydroxyproline production of the respective each cell lines was not correlated with the growth rate, but it showed a close correlation with saturation densities.
5. All clones were highly PTH-responsive and human PTH (1-34, 10^<-8>M) stimulations on their cyclic AMP level ranged between 1.2-fold and 7-fold of the MSK cells.
6. All clonal lines showed significant response to PTH, and particularly C5.4E. One of the remarkable characteristics of C5.4E, as compared with the other clonal strains, was to contain large amounts of chondroid in reproducing tumor in vivo. Although recent studies have indicated that the PTH responsiveness is noe of the major characteristics of osteoblasts and/or ostoblast-like cell, it is still not clear as to which cells actually respond to PTH in the course of the differentiation stage of osteoblastic linkage. Some studies have documented the relation between PTH and the chondrogenic cell population. Our results with C5.4E also suggest this relationship.
7. High collagenase activity was detected in conditioned medium of clonal cell lines.
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