title: Role of Ca2+ and cyclic AMP in the regulation of the production of prostacyclin by the vascular endothelium.
abstract: Incubation of primary monolayer cultures of human umbilical vein endothelial cells with buffer, thrombin (0.5 unit/ml), ionophore A23187 (10 microM), arachidonic acid (20 microM), prostaglandin H2 (PGH2) (4 microM) resulted in prostacyclin (PGI2) production in nanomolar quantities to the extent of 36 +/- 2, 276 +/- 13, 485 +/- 32, 533 +/- 22, and 532 +/- 22, respectively, as measured by radioimmunoassay of 6-keto-PGF alpha. Preincubation of the endothelium with 1 mM 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate, an antagonist of cytoplasmic Ca2+, or with 4 mM 1-methyl-3-isobutylxanthine (MIX), an inhibitor of cyclic nucleotide phosphodiesterase activity, blocked PGI2 release induced by thrombin or A23187, decreased arachidonic acid-induced release by approximately 50%, but had no effect on PGH2-induced release. Radioimmunoassay of cAMP in the endothelium showed that the basal level (1.85 +/- 0.14 pmol of cAMP per 4.5 x 10(5) cells) was increased by an average of 3.9-fold with 4 mM MIX. PGI2 (0.4 microM) had no significant effect on cAMP levels in the absence of MIX, but caused a 2-fold increase with 4 mM MIX. The findings suggest that: (i) the stimulation of PGI2 biosynthesis is mediated by Ca2+, (ii) increased cAMP inhibits PGI2 production, and (iii) cAMP phosphodiesterase activity modulates PGI2-induced increases in the intracellular concentration of cAMP.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology*; D004727:Endothelium / Q000378:metabolism*; D011464:Epoprostenol / Q000096:biosynthesis*; D006801:Humans; D011453:Prostaglandins / Q000096:biosynthesis*; D011463:Prostaglandins H / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D014471:Umbilical Veins
chemical_list: D001095:Arachidonic Acids; D011453:Prostaglandins; D011463:Prostaglandins H; D016718:Arachidonic Acid; D000001:Calcimycin; D011464:Epoprostenol; D000242:Cyclic AMP; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D013917:Thrombin; D002118:Calcium