Effects of prostaglandin E2 and F2α on cytoplasmic pH in a clonal osteoblast-like cell line, MOB 3–4

✍ Scribed by Tomoyuki Kawase; Michiaki Orikasa; Akitoshi Suzuki

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 816 KB
• Volume: 146
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041460118

✦ Synopsis

Prostaglandin E, (PGE,, 5 ng/ml to 5 pg/ml) induced a dose-dependent increase in cAMP accumulation, inositol phosphates (IPS) accumulation, and cytoplasmic free Ca2+ ([Ca2+li) in a clonal osteoblast-like cell line, MOB 3-4. In contrast, prostaglandin F,a (PGF a, 5 ng/ml to 5 p,g/ml) stimulated increases in IPS accumulation and ICa';L]i without stimulating an increase in cAMP accumulation. Both PGE, P 0 . 5 pg/ml) and PGF,a (30.5 p,g/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 PGE,-(5 pg/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 FM), a nonspecific inhibitor of protein kinase C. Thus, MOB 3-4 cells appeared to possess PGE, receptors and PGF,a 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 PGE, and PGF,a, as well as to PMA. Long-term (48 hr) exposure of the cells to PGE, at a high concentration (5 pg/ml), but not to PGFp 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 PGE, on DNA synthesis may be due to the cAMP messenger system.