epidermal-growth-factor and inositol-1-phosphate

This study investigated the effects of epidermal growth factor (EGF) on cytosolic calcium ([Ca++]i) levels in rat calvarial osteoblasts, the nature of the regulation of this event, and the role these EGF-induced [Ca++]i changes have in osteoblastic cell proliferation. EGF significantly increased [Ca++]i measured in fura-2-loaded, individual cells. This increase was related to extracellular calcium influx. Activation of protein kinase C(PKC) by pretreating the cells with phorbol esters blocked the EGF-induced increase in [Ca++]i. EGF failed to increase inositol trisphosphate levels measured by high performance liquid chromatographic analysis. However, it did increase inositol bisphosphate and inositol tetrakisphosphate production. The EGF-dependent increase in DNA synthesis was partially blocked by the addition of calcium channel blockers. Therefore, it appears that the mechanism of action of EGF-induced osteoblastic cell proliferation is mediated by changes in [Ca++]i primarily due to extracellular calcium influx.

Topics: Analysis of Variance; Animals; Calcium; Calcium Channel Blockers; Cell Division; Cells, Cultured; Chromatography, High Pressure Liquid; Cytosol; DNA; Enzyme Activation; Epidermal Growth Factor; Fura-2; Inositol 1,4,5-Trisphosphate; Inositol Phosphates; Osteoblasts; Protein Kinase C; Rats; Rats, Sprague-Dawley; Tetradecanoylphorbol Acetate