INFLUENCE OF COINCUBATION AND CELL NUMBER OF PLATELETS AND POLYMORPHONUCLEAR LEUKOCYTES IN CELLULAR-INHIBITION AND ACTIVATION PHENOMENA

Evidence indicates that complex interactions occur between blood platelets and polymorphonuclear leukocytes PMN) referring to both activation and inhibition phenomena. We studied the influence of co-incubating activated PMN and platelets at varying cell counts in the production of two active metabolites, thromboxane A, (TxA(2)) measured as thromboxane B-2 (TxB(2)) and platelet activating factor (PAF). The decrease observed in the quantity of TxA(2) synthesized by 2x10(8) platelets/ml in the presence of physiological PMN counts clearly indicates an inhibitory effect of PMN in AA-derived metabolites. This suggests there is an influence of PMN-released products on activated platelets, decreasing their capacity to synthesize TxA,. Moreover, we found that the addition of platelets, which do not make measurable quantities of PAF, to PMN suspensions significantly decreased the capacity of PMN to synthesize this mediator. Together with this inhibiting action we also observed an activating effect, in such a way that the more PMN were added to platelet suspensions the more TxA, was produced. Conversely, the maximal amounts of PAF were synthesized when the highest platelet count suspensions were added to PMN. In summary, the results we present here clearly show cellular interactions between platelets and PMN that directly influence the amounts of metabolites synthesized by both cells.