A B S T R A C T Bovine aortic endothelial and smooth muscle cells in culture were incubated with arachidonic acid or prostaglandin H2. The amouint of prostacyclin and thromboxane A2 synthesized was then determined by specific radioimmunoassay for 6-keto-prostaglandin F1, and thromboxane B2. Although smooth muscle cells produced only 6-keto-prostaglandin Fi,,a, endothelial cells produced 6-keto-prostaglandin F,af and thromboxane B2 in a ratio of 5:1 to 10:1. The same ratio of these metabolites of arachidonic acid was also found when prostaglandin production from endogenous arachidonic acid was stimulated in endothelial cells by the ionophore A23187. Cyclooxygenase inhibitors inhibited the prodtuction of both metabolites equially, whereas thromboxane synthetase inhibitors selectively inhibited the production of thromboxane B2. Cells in culture were also incubated with [1-14C]arachidonic acid and the extracted products were identified by twodimensional thin-layer chromatography. 6-Keto-prostaglandin Flat was the only metabolite produced by smooth muscle cells, but endothelial cells synthesized 6-keto-prostaglandin Fla, thromboxane B2, prostaglandin E2, and prostaglandin F2a.

SummaryPatients who present with a clinical history suggesting a bleeding disorder are often tested initially for a clotting defect rather than for platelet dysfunction, due to the length of time necessary to complete a platelet function study in platelet-rich plasma. We have developed a sensitive method for measuring platelet aggregation and release of ATP employing the Whole Blood Lumi-Aggregometer. This method makes it possible to quickly detect patients who require further study for possible platelet function disorders such as cyclooxygenase deficiency, storage-pool defect, thrombasthenia, and von Willebrand’s disease. The results obtained with this electrical impedance instrument do not differ from those obtained with the conventional optical method. However, it is now possible to recognize a platelet function defect within 30 min of obtaining a 5 ml sample of citrated whole blood. Further, platelets of unusual size or density are not lost to testing through centrifugation.

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