Effect of prostanoids and their precursors on the aggregation of rainbow trout thrombocytes
Hill, D.J.; Hallett, M.B.; Rowley, A.F.
American Journal of Physiology 276(3): R659-R664
1999
ISSN/ISBN: 0002-9513 PMID: 10070125 Document Number: 498209
The role of prostanoids and their precursor fatty acids in the aggregatory response of thrombocytes (platelet equivalents of fish) from the rainbow trout, Oncorhynchus mykiss, was studied. Aggregation of these cells was induced by the thromboxane mimetic U-46619 or arachidonic acid (AA) in the presence of human or trout fibrinogen. The production of TXB2/3 by thrombocytes in response to stimulation with AA was inhibited by aspirin, ibuprofen, and indomethacin. However, thrombocyte aggregation in response to AA stimulation was not significantly altered by these agents at the concentrations tested (10-100 mM), with the exception of indomethacin at 20 and 40 mM. Effects on cytosolic calcium concentration have been suggested as an alternative mechanism for the inhibitory action of indomethacin on human platelet aggregation. The present study, however, failed to identify this as a mechanism for the inhibition of U-46619-induced trout thrombocyte aggregation by indomethacin. The polyunsaturated fatty acids docosahexaenoic acid and eicosapentaenoic acid both exhibited an inhibitory effect on U-46619-induced thrombocyte aggregation similar to that observed with mammalian platelets. Unlike the case in mammalian hemostasis, prostacydin inhibited thrombocyte aggregation only at high concentrations (>5 mM). Prostaglandin E2, however, inhibited thrombocyte aggregation at much lower concentrations (>0.01 mM), suggesting that it may be the major inhibitory eicosanoid in trout. Reprinted by permission of the publisher.