title: Elevation of intracellular calcium ion by prostaglandin E1 and its inhibition by protein kinase C in a human megakaryocyte leukemia cell line.
abstract: In the present study, we examined the effect of prostaglandin E1 (PGE1) on Ca2+ mobilization in a human megakaryocyte (the progenitor of platelets) leukemia cell line, designated as CMK. PGE1 caused a rapid and dose-dependent increase in the intracellular free calcium level ([Ca2+]i) associated with the elevation of cyclic AMP. The PGE1-induced elevation of [Ca2+]i was decreased by the prior addition of ethylene glycol bis(2-aminoethylether)tetraacetic acid to the medium by approximately 25% of the control. This result indicates that the PGE1-induced elevation of [Ca2+]i is due to influx of Ca2+ from the external medium and to mobilization of Ca2+ from intracellular stores. Pretreatment of CMK cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), a stimulus for protein kinase C, further enhanced the PGE1-induced increase in the cellular cyclic AMP level. Inversely, pretreatment of CMK cells with TPA (10 nM), prior to the addition of PGE1, inhibited the PGE1-induced elevation of [Ca2+]i. Dibutyryl cyclic AMP and forskolin did not elevate [Ca2+]i or affect the PGE1-induced Ca2+ mobilization. The inhibitory action of TPA in the PGE1-induced elevation of [Ca2+]i was mimicked by other protein kinase C-activating agents, such as 1-oleoyl-2-acetylglycerol and N-(6-phenylhexyl)-5-chloro-1-naphthalenesulfonamide, and was selectively restored by protein kinase C inhibitors, such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride and N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride. Thus, the inhibitory modulation of TPA on the PGE1-induced elevation of [Ca2+]i is mediated through protein kinase C activation. PGE1 had no inductional effect of megakaryocytic phenotypic changes in CMK cells. The biological role of PGE1, which increased [Ca2+]i and cyclic AMP levels in the CMK cells, remains to be determined.
authors.affiliation: Department of Laboratory Medicine, Kobe University School of Medicine, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Adachi
authors.forename: R
authors.initials: R
authors.lastname: Ryo
authors.forename: A
authors.initials: A
authors.lastname: Yoshida
authors.forename: K
authors.initials: K
authors.lastname: Teshigawara
authors.forename: N
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: M
authors.initials: M
authors.lastname: Hoshijima
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
authors.forename: T
authors.initials: T
authors.lastname: Sato
mesh_terms: D000527:Alprostadil / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013920:Thrombocythemia, Essential; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism*
chemical_list: D011493:Protein Kinase C; D000527:Alprostadil; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium