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.
Carpio
L C
LC
Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, 14214, USA.
Dziak
R
R
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