Measurement Of 1-14C Arachidonic Acid Metabolism By Cultured Human Vascular Endothelial Cells And Platelets
To investigate the relative sensitivity of endothelial cells and platelets towards aspirin (ASA), a method was designed which allows the measurement of prostaglandin (PG) metabolism using [l-14C] arachidonic acid (AA) as precursor. When HEC were incubated with 20 μM AA for 24h at 37°C in the presence of serum, about 15-20% of the label was incorporated into phospholipids whereas 3-4% was present in the neutral lipid fraction. No PG formation could be measured, even after stimulation of the phospholipase system by thrombin or ionophore A 23187. When HEC were incubated for 20 min with AA in the absence of serum, about 8-10% of the label was incorporated into PGs (6-keto PGF1α, 2%; PGE2, 1%; PGF2α, 4%). Platelets were prelabeled with AA, in buffer and the phospholipase system could be stimulated by thrombin (measured as the formation of TXB2, HHT and HETE). Using the above methods, the IC50 of ASA (30 min, 37°C) was 4.7±2.4μM for HEC and 10.1±2.4μM for platelets (p>0.1). Preincubation with 5μM ASA resulted in 50% inhibition of PG synthesis after 30±8 min with HEC and after 40±5.6 min with platelets (p#x003E;0.1). Moreoever when HEC and platelets were combined, incubated with ASA and subsequently tested separately no difference in dose-response curves could be demonstrated. These results indicate that the sensitivity of HEC and platelets to ASA is similar.