Parathyroid hormone stimulates phosphoinositide metabolism and intracellular calcium mobilization in osteoblast-like clone MC3T3-E1 cells

The effects of parathyroid hormone (rat 1–34 fragment, rPTH) on phosphoinositide metabolism and intracellular Ca²⁺ mobilization were studied in a osteoblast-like clone MC3T3-E1 cells. rPTH caused a transient rise in intracellular Ca²⁺ in a dose-dependent manner. Significant Ca²⁺ increase was still observed under the extracellular Ca²⁺-free condition. In addition, 100nM rPTH stimulated rapid formation of both 1,2-diacylglycerol (1,2-DAG) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P₃), indicating agonist-triggered hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP₂). The current observations suggested that the rPTH-induced increase of intracellular Ca²⁺ was in part due to internal Ca²⁺ release mediated by Ins(1,4,5)P₃. These results indicate possible involvement of phosphoiniositide metabolism in signal transduction of PTH-stimulated osteoblastic cells.