Evaluation of inhibitors of the arachidonic acid cascade with intact platelets using an on-line dilution and on-line...

An automatic on-line dilution/on-line solid phase extraction (SPE) system has been developed for the detection of metabolites of the arachidonic acid cascade in platelets. The method allows the direct injection of larger quantities of centrifugates from cell suspensions previously treated with an equal volume of an acetonitrile/methanol mixture for protein precipitation. The method was used to study the effect of inhibitors of platelet arachidonic acid cascade enzymes (cytosolic phospholipase A₂α, cyclooxygenase-1, thromboxane synthase, 12-lipoxygenase) and related targets (cyclooxygenase-2, microsomal prostaglandin E synthase-1, 5-lipoxygenase) in intact platelets after stimulation with calcium ionophore A23187. In addition to enzyme inhibition, the cell-damaging properties of the test compounds was determined by measuring the release of serotonin from the platelets into the incubation buffer.