Phosphatidic acid effects on cytosolic calcium and proliferation in osteoblastic cells.
Our previous studies show that epidermal growth factor (EGF) stimulates phospholipase D (PLD)-induced phosphatidic acid (PA) formation in rat calvarial osteoblastic cells. This study investigated the effects of PA on cytosolic calcium ([Ca2+]i) and proliferation, and the possible involvement of the PLD pathway in EGF effects on [Ca2+]i and proliferation in rat calvarial osteoblastic cells. PA markedly increased [Ca2+]i. This response was unaffected by thapsigargin, which depletes [Ca2+]i pools, blocked by verapamil, a calcium channel blocker, and enhanced by propanolol, an inhibitor of PA-phosphohydrolase. PA also reduced the EGF dependent-[Ca2+]i increase by 60%, while a PLD inhibitor blocked these effects. Furthermore, PA significantly increased cell proliferation (P < 0.05) which was inhibited by verapamil and enhanced by H-7 (PKC inhibitor). The PLD inhibitor significantly (P < 0.05) reduced the EGF-induced increase in proliferation. In summary, PA stimulates rat calvarial osteoblastic cell proliferation and mobilization of [Ca2+]i using extracellular pools, and EGF's mitogenic effect on these cells requires activation of PLD.
Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, 14214, USA.
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010712:Phosphatidic Acids / Q000494:pharmacology* / Q000502:physiology; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012886:Skull / Q000166:cytology; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D010712:Phosphatidic Acids; D004815:Epidermal Growth Factor; D019284:Thapsigargin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011433:Propranolol; D014700:Verapamil; D011493:Protein Kinase C; D010739:Phospholipase D; D013110:Sphingosine; C005682:safingol; D002118:Calcium