Existence of parathyroid hormone binding sites on murine hemopoietic blast cells

We demonstrated that 125I-labeled human parathyroid hormone (1–34;8,18-Nle, 34-Tyr)[[ 125I]hPTH(1–34)] bound specifically to hemopoietic blast cells supported by granulocyte-macrophage colony-stimulating factor. Half-maximal inhibition of binding was achieved at concentrations of unlabeled hPTH(1–34) of about 5 × 10 −9M. Insulin and hPTH(39–68) did not compete for PTH binding sites. Specific binding of hPTH(1–34) was detected in neither macrophages nor multinucleated cells (MNC's). Furthermore, treatment of hemopoietic blast cells with hPTH(1–34) stimulated MNC formation, and the range of concentrations (10 −10–10 −8M) over which hPTH(1–34) caused these effects was similar to that which inhibited the binding of [ 125I]hPTH(1–34). These findings suggest the presence of a PTH receptor on osteoclast precursors and the direct effect of PTH on them, resulting in osteoclast-mediated bone resorption.