PT - JOURNAL ARTICLE AU - M D Nyby AU - M Sasaki AU - Y Ideguchi AU - H E Wynne AU - M T Hori AU - M E Berger AU - M S Golub AU - A S Brickman AU - M L Tuck TI - Platelet lipoxygenase inhibitors attenuate thrombin- and thromboxane mimetic-induced intracellular calcium mobilization and platelet aggregation. DP - 1996 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 503--509 VI - 278 IP - 2 4099 - http://jpet.aspetjournals.org/content/278/2/503.short 4100 - http://jpet.aspetjournals.org/content/278/2/503.full SO - J Pharmacol Exp Ther1996 Aug 01; 278 AB - Platelets metabolize arachidonic acid via cyclooxygenase and lipoxygenase (LO) enzymatic pathways. Although platelets produce large amounts of arachidonic acid metabolites via the LO pathway, little is known regarding the physiological significance of these products. We used three structurally dissimilar LO inhibitors, 5,8,11-eicosatriynoic acid (ETI), baicalein and phenidone, and found that LO inhibition attenuated thrombin- and U46619 (a thromboxane mimetic)-induced increases of platelet intracellular calcium ([Ca++]i) in washed human platelets. LO inhibitors also reduced platelet aggregation induced by thrombin and U46619. The effect of ETI on reducing the thrombin-induced [Ca++]i elevation persisted even when cation channels were blocked, suggesting that LO inhibitors modify release of Ca from intracellular stores. Stimulating endogenous LO product formation potentiated thrombin-induced [Ca++]i responses and aggregation, and these effects were eliminated by ETI. ETI did not alter inositol 1,4,5-trisphosphate production in stimulated platelets, but increased platelet cyclic AMP production in thrombin- or forskolin-stimulated platelets. These results suggest that LO products are regulators of platelet [Ca++]i mobilization and aggregation in response to some agonists, and that LO inhibitors may work in part by modifying platelet cyclic AMP metabolism.