Human Platelet Secreted Proteins and Prostacyclin Production by Bovine Aortic Endothelial Cells 1 2

Abstract

The effects of specific human platelet-secreted proteins on prostacyclin (PGI₂) production by primary cultures of bovine aortic endothelial cells have been studied. Cells were incubated with various concentrations of highly purified preparations of platelet factor 4(PF₄), low-affinity platelet factor 4 (LA-PF₄), β-thromboglobulin (βTG), platelet basic protein (PBP), and partially purified plateletderived growth factor (PDGF) in the presence or absence of arachidonic acid (AA). The amount of 6-Keto-PGF_1α, the stable degradation product of PGI₂, was determined in the cell incubation medium by means of a specific radioimmunoassay. Short-term (15 min) incubation of cell monolayers with either LA-PF₄ or βTG slightly reduced 6-keto-PGF_1α production. The effect was not dose-related and could not be observed after prolonged (24 hr) incubation of the cells with the same proteins. It was not seen in the cell suspensions. Moreover, 6-keto-PGF_1α production stimulated by AA was not affected by incubation with either of the proteins. PF₄ and PBP had no significant effect on 6-keto-PGF_1α production by endothelial cells. Human PDGF showed a slight tendency to stimulate 6-keto-PGF_1α release when cells were incubated for 24 hr with the protein; however, PDGF did not potentiate the stimulatory effect of AA on 6-keto-PGF_1α release by the cells. We suggest that plateletderived proteins exert only a moderate and possibly nonspecific effect on PGI₂ production by endothelial cells.