Effects of prostaglandin E2 and F2 alpha on cytoplasmic pH in a clonal osteoblast-like cell line, MOB 3-4.
Prostaglandin E2 (PGE2, 5 ng/ml to 5 micrograms/ml) induced a dose-dependent increase in cAMP accumulation, inositol phosphates (IPs) accumulation, and cytoplasmic free Ca2+ ([Ca2+]i) in a clonal osteoblast-like cell line, MOB 3-4. In contrast, prostaglandin F2 alpha (PGF2 alpha, 5 ng/ml to 5 micrograms/ml) stimulated increases in IPs accumulation and [Ca2+]i without stimulating an increase in cAMP accumulation. Both PGE2 (greater than 0.5 micrograms/ml) and PGF2 alpha (greater than or equal to 5 micrograms/ml) increased cytoplasmic pH (pHi) from approximately 7.15 to 7.35 in BCECF-loaded cells. A tumor promotor, phorbol 12-myristate 13-acetate (PMA, 0.1-100 nM) also increased pHi without effect on phosphoinositide hydrolysis. Both PGE2-(5 micrograms/ml) and PMA- (100 nM) induced cytoplasmic alkalinization was inhibited by removal of extracellular Na+, or by pretreatment of the cells with amiloride (0.5 mM), an inhibitor of Na+/H+ exchange, or H-7 (100 microM), a nonspecific inhibitor of protein kinase C. Thus, MOB 3-4 cells appeared to possess PGE2 receptors and PGF2 alpha receptors: the former are coupled to adenylate cyclase and phospholipase C, and the latter are predominantly coupled to phospholipase C. Also the cells appeared to possess an amiloride-sensitive Na+/H+ exchange activity, which increases pHi in response to PGE2 and PGF2 alpha, as well as to PMA. Long-term (48 hr) exposure of the cells to PGE2 at a high concentration (5 micrograms/ml), but not to PGF2 alpha and PMA, decreased DNA synthesis in the serum-deficient medium. Thus, cytoplasmic alkalinization appeared insufficient for cell replication. At least in MOB 3-4 cells, the inhibitory effect of PGE2 on DNA synthesis may be due to the cAMP messenger system.
Kawase
T
T
Department of Pharmacology, Niigata University School of Dentistry, Japan.
Orikasa
M
M
Suzuki
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002999:Clone Cells; D000242:Cyclic AMP / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects; D015237:Dinoprost / Q000502:physiology*; D015232:Dinoprostone / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007295:Inositol Phosphates / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007295:Inositol Phosphates; D015237:Dinoprost; D000242:Cyclic AMP; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium