ARACHIDONIC-ACID METABOLISM IN PLATELETS STORED FOR 5 DAYS

(C‐14)‐Arachidonic acid [(C‐14)‐AA] metabolism was studied in platelet concentrates (PCs) stored for 5 d. There was a gradual decrease in uptake of radioactivity from day 0 to 3 (P < 0.01). On day 0, distribution of radioactivity in platelet phospholipids (PLs), and formation of phosphatidic acid, HETE and cyclooxygenase products, when platelets were exposed to thrombin (5 U/ml), were similar to that reported for fresh platelets. On day 3 there was a change in the distribution of (C‐14)‐AA in platelet PLs which consisted of an increase in the percentage of radioactivity bound to phosphatidylserine, from 5.3±0.9% on day 0 to 8.8±1.5% on day 3 (P<0.001), and a decrease in (C‐14)‐AA in phosphatidylinositol (PI), from 12.4±1.5% on day 0, to 7.9±0.9% on day 3 (P<0.001). Phosphatidic acid generated by thrombin‐stimulated platelets on day 0, comprised 2.6±0.5% of total radioactivity, but dropped to 1.4±0.3% on day 3 (P<0.001), and 0.9±0.2% on day 5 (P<0.01). These values showed a good correlation with the percentage of (C‐14)‐AA released from PI on the same days (r=0‐9). On day 0, 13.4 ± 4.4% of platelet radioactivity was released from phosphatidylcholine by thrombin, but this amount was reduced to 6.8±3.4% on day 5 (P<0.05). Generation of radioactive 12‐hydroxy‐5,8,10,14‐eicosatetraynoic acid (HETE) also dropped from 7.2±2.9 on day 0. to 2.1 ± 1 on day 5 (P< 0.01). We could not detect changes in cyclooxygenase metabolites. In conclusion, we suggest that various enzymatic pathways implicated in AA metabolism by platelets are impaired by storage. Copyright © 1990, Wiley Blackwell. All rights reserved