Synthesis of prostaglandin I2 (prostacyclin) by cultured human and bovine endothelial cells.

Abstract

Cultured endothelial cells derived from human umbilical veins or bovine aorta produce a potent inhibitor of platelet aggregation. The inhibitor is synthesized from sodium arachidonate or prostaglandin endoperoxides by a microsomal enzyme system. Tranylcypromrine, a specific antagonist of prostacyclin synthetase, suppresses production of the inhibitor by endothelial cells. The inhibitor, which is ether extractable, has been identified using a two-step thin-layer radiochromatographic procedure and a synthetic prostaglandin I2 standard. With this procedure, we have shown that human and bovine endothelial cells convert sodium [3H]arachidonate to radiolabeled prostaglandin I2 and 6-keto-prostaglandin Fla, as well as prostaglandin E2. Thus, endothelial cells may be non-thrombogenic in vivo because they synthesize and release prostaglandin I2, a potent inhibitor of platelet aggregation.Fragments of blood vessel walls acting upon prostaglandin (PG) endoperoxides or arachidonic acid produce an unstable factor that prevents platelet aggregation and release (1, 2). This factor, recently identified as (5Z)-9-deoxy-6,9-a-epoxy A5-PGFIa, (prostacyclin L-glutamine (2 mM). Cells were grown in T-25 or T-75 flasks (Corning) at 370 under 5% C02/95% air until confluence. Both primary cultures and serial passages were utilized. Initial cultures of bovine endothelial cells were kindly provided by Alan Quarfoot and Francois Booyse (13) and were cultured in RPMI 1640 medium containing 10-20% heat-inactivated fetal calf serum and penicillin, streptomycin, and L-glutamine as above. Cells were harvested from culture flasks by treatment with 0.1% collagenase-0.01% EDTA for 10 min at 370, washed three times in buffer A [137 mM NaCl/4 mM KCl/11 mM glucose/10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (Hepes), pH 7.5] and finally resuspended in the same buffer at 6 X 106 cells per ml.Culture and Preparation of Other Cells. Human fibroblasts were grown in tissue culture, harvested with trypsin (0.25%) for 10 min, washed similarly, and resuspended in buffer A at the same protein concentration as the endothelial cells. Peripheral blood mixed leukocytes (70-80% neutrophils) were separated from heparin-treated whole blood by dextran sedimentation, washed, and resuspended in-buffer A at a similar protein concentration.Platelet Aggregation Experiments. Platelet-rich plasma (PRP) was prepared from venous blood drawn into 'ho volume of 3.2% trisodium citrate by methods previously described (14) and was kept tightly capped at 220 under 5% C02/95% air until use. Compounds being tested (0.1 ml) were added to 0.4 ml of PRP in the cuvette of a Payton aggregation module (Payton Associates, Buffalo, NY). Aggregating agents used included arachidonic acid (as the sodium salt in 0.1 M Na2COA), adenosine diphosphate (ADP) and collagen (Sigma Chemical Co., St. Louis, MO), and bovine thrombin (Parke Davis Co., Detroit, MI). Synthetic PGI2 (15) final volume of 0.5 ml in an aggregation module cuvette at 370 Abbreviations: PG, prostaglandin; ...

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

“…Endothelial cells also synthesise tissue factor pathway inhibitor, which plays an important role in the down-regulation of the initial phase of coagulation [61], and protein S, which is a co-factor to APC and thereby promotes the anticoagulant activity of APC [62]. In addition to these anticoagulant and profibrinolytic effects, EC can also control the reactivity of platelets via synthesis of ecto-adenosine diphosphatase [63], prostaglandin I 2 [64] and nitric oxide (NO), also known as endothelium-derived relaxing factor [65].…”

Myocardial Synthesis of Prostaglandin‐like Substances and Coronary Reactions to Cardiostimulation and to Hypoxia

“…1977) to be a likely candidate for the location of prostaglandin-synthetase. Moreover, endothelial cells synthesize and release prostaglandins from AA (Weksler, Marcus & Jaffe, 1977) and in all these instances indomethacin, or other nonsteroidal anti-inflammatory agents block the conversion of AA to prostaglandins (Flower,1q75).…”

Activation of Rabbit Hageman Factor by Homogenates of Cultured Rabbit Endothelial Cells

“…Endothelial cells are known to produce enzymes that activate plasminogen (1, 2), procoagulant molecules such as tissue factor (36), and factors that influence platelet function and vascular tone (3)(4)(5)(6)(7). We now report the capacity of this cell type to activate HF.…”

“…The compatibility of the intact endothelial cell surface with blood and its constituent procoagulant proteins is a central and necessary condition for maintenance ofvascular homeostasis. Although the mechanism of this compatibility has not been fully elucidated, it is clear that the production by endothelial cells of fibrinolytic enzymes (1,2), prostacyclin (3), and other factors that influence platelet function (4,5) or vascular tone (6) may play a significant role in ensuring vessel patency. The endothelial cell surface is equally important in hemostasis and the induction of thrombus formation inasmuch as damage to this layer is associated with attachment of platelets and the initiation of coagulation (7).…”