title: Inhibition of prostaglandin E2-induced phosphoinositide metabolism by phorbol ester in bovine adrenal chromaffin cells.
abstract: In bovine adrenal chromaffin cells, prostaglandin E2 (PGE2) stimulates the formation of inositol phosphates and Ca2+ mobilization through its specific receptor [Yokohama, Tanaka, Ito, Negishi, Hayashi & Hayaishi (1988) J. Biol. Chem. 263, 1119-1122]. Here we show that PGE2-induced phosphoinositide metabolism was blocked by pretreatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). Using intact cells, we also examined the inhibitory effect of TPA on the individual steps of the activation process of phosphoinositide metabolism. The inhibition was observed within 1 min and complete by 10 min after addition of 1 microM-TPA, and half-maximal inhibition by TPA occurred at 20 nM. TPA prevented Ca2+ mobilization induced by PGE2, but not by the Ca2+ ionophore ionomycin. The inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate did not inhibit the formation of inositol phosphates and Ca2+ mobilization by PGE2. TPA treatment affected neither the high-affinity binding of [3H]PGE2 to intact cells and membrane fractions nor the ability of guanosine 5'-[gamma-thio]triphosphate to decrease the binding in membrane fractions. TPA also abolished phosphoinositide metabolism induced by muscarinic-receptor activation. NaF plus AlCl3 and ionomycin caused the accumulation of inositol phosphates, probably by directly activating a GTP-binding protein(s) and phospholipase C respectively; neither accumulation was inhibited by TPA treatment. These results suggest that protein kinase C serves as a feedback regulator for PGE2-induced phosphoinositide metabolism. The site of action of TPA appears to be distal to the coupling of the receptor to GTP-binding protein, but on a component(s) specific to the agonist-induced phosphoinositide metabolism.
authors.affiliation: Hayaishi Bioinformation Transfer Project, Research Development Corporation of Japan, Kyoto.
authors.forename: H
authors.initials: H
authors.lastname: Yokohama
authors.forename: M
authors.initials: M
authors.lastname: Negishi
authors.forename: K
authors.initials: K
authors.lastname: Sugama
authors.forename: H
authors.initials: H
authors.lastname: Hayashi
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.forename: O
authors.initials: O
authors.lastname: Hayaishi
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002837:Chromaffin Granules / Q000187:drug effects / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology*; D007295:Inositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
chemical_list: D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D010738:Type C Phospholipases; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium