[Studies of aggregation using pairs of agonists in platelet concentrates stored for 5 days. Influence of autologous fresh plasma].

Aggregation was studied with synergistic agents on platelets stored for 5 days. Fixed concentrations of agonist agents, capable of inducing maximum response upon platelet concentrate (PC) preparations were used, and the results were compared with those achieved from samples previously incubated in fresh autologous plasma. Platelet aggregation on day 0 ranged between 77 +/- 3% with the combination epinephrine/ADP and 72 +/- 7% with collagen/ADP, these figures decreasing by the fifth day to 14 +/- 5% and 10 +/- 4%, respectively. The other paired aggregation agents were epinephrine/collagen and arachidonic acid (AA)/ADP; with these agents, similar values were attained on day 0, along with an analogous derangement of the response by the fifth day. With the last combination, the aggregation value attained on days 3 was 14 +/- 10% in experiments with the PC plasma, as opposed to 49 +/- 15% in assays with fresh plasma (p less than 0.001). Such difference persisted on day 5 and was thought to be due to competence of the high concentration of fatty acids generated in the PC plasma by AA. No differences induced by fresh plasma on the other agonist combinations were detected. These results suggest that some derangement of platelet function, conditioned by nonreversible alterations, and measured by paired agonist aggregation, may derive from storage.