6-ketoprostaglandin-f1-alpha and isosorbide-5-mononitrate

In an experimental model in which cultured endothelial cells (EC) and platelets were incubated with autologous plasma, we investigated the pharmacological modulations by isosorbide nitrates (ISN) [isosorbide dinitrate (ISDN) + 2-isosorbide mononitrate (2-ISMN) + 5-ISMN] of the EC-induced inhibition of platelet aggregation; and the associated changes in prostanoid profile of these mixed EC-platelet suspensions. ISDN antiplatelet activities were found to be magnified profoundly by EC, being dependent upon both ISDN concentration and EC number, e.g., 5.10(-5) M ISDN in the presence of 2.10(4) cells, fully arrested ADP-induced aggregation, whereas the same ISDN concentration induced 30% inhibition in control platelet activities. In contrast, there were no significant changes in 2- and 5-ISMN antiaggregating properties, whether incubated in the presence or absence of EC. Thromboxane B2 accumulated noticeably after aggregation, whereas 6-keto-prostaglandin (PG) F1 alpha and PGE2 accumulated poorly in the medium. In the presence of EC, thromboxane B2 accumulation fell in parallel to the extent of aggregation, whereas 6-keto-PGF2 alpha and PGE2 accumulated in the medium. Aspirin-treated, washed ECs still inhibited platelet aggregation. ISDN was the only ISN capable of inducing PG-accumulation profile changes. These results demonstrate the existence of an endothelium-dependent ISDN antiplatelet activity. Furthermore, this effect is specific to ISDN not being shown by its mononitrate metabolites. These results suggest that PG accumulation changes may be a consequence rather than a cause of the inhibition of platelet activity by (ISDN-stimulated) EC.

Topics: 6-Ketoprostaglandin F1 alpha; Adenosine Diphosphate; Adult; Arachidonic Acid; Arachidonic Acids; Cell Extracts; Cells, Cultured; Dinoprostone; Endothelium; Female; Humans; Isosorbide Dinitrate; Male; Platelet Aggregation; Prostaglandins E; Thromboxane B2; Tissue Extracts

The hypothesis that nitrates evoke prostacyclin production by vascular endothelium has been reevaluated on cultured umbilical vein endothelial cells and in vascular fragments, both obtained from humans. Endothelial cell monolayers (passages 1 and 2) were washed free of culture medium and exposed for 3 to 5 min to buffer or nitroglycerin (NTG), isosorbide dinitrate (ISDN), or isosorbide-5-mononitrate (ISMN) over a range of concentrations (10(-9)M to 10(-6)M) encompassing those usually attained in vivo, with or without 25 microM sodium arachidonate. Basal prostacyclin production, measured by radioimmunoassay of the stable metabolite 6-keto-PGF1 alpha, depended on cell density in the endothelial monolayer (being higher in preconfluent cultures) and on incubation time. Basal prostacyclin, however, was not altered by incubation with NTG (3.3 +/- 2.0 pg/1000 cells without drug vs 3.9 +/- 3.8 pg/1000 cells with drug, mean +/- SD), ISDN (3.1 +/- 1.9 vs 3.1 +/- 2.2), or ISMN (2.0 +/- 0.9 vs 2.3 +/- 1.5) at 10(-7)M (all differences NS). Also, long-term incubation (2, 6, and 24 hr) with ISDN and ISMN did not alter prostacyclin production over control. Over a 30-fold increase (p less than .001) in prostacyclin production was obtained with arachidonate stimulation, but incubation with nitrates did not significantly modify the stimulated production. Saphenous vein, mesenteric artery, and atrial appendage fragments incubated at 37 degrees C for 20 min in a shaking water bath with a control buffer produced 27.8 +/- 13.9, 189.7 +/- 75.2, and 662.3 +/- 390.6 pg 6-keto-PGF1 alpha/mg tissue, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 6-Ketoprostaglandin F1 alpha; Blood Vessels; Cells, Cultured; Endothelium; Epoprostenol; Humans; In Vitro Techniques; Isosorbide Dinitrate; Nitrates; Nitroglycerin; Thromboxane B2; Vasodilator Agents