Heparin enhances thrombin-stimulated prostaglandin I2 production by cultured endothelial cells

Endothelial cells from human umbilical vein were incubated in vitro with thrombin in the absence or presence of unfractionated heparin (UFH), low molecular weight heparin (LMWH) or dermatan sulfate (DS) to clarify the effect of these glycosaminoglycans on thrombin-stimulated prostaglandin I2 (PGI2) production. Although DS did not affect the thrombin stimulation, UFH and LMWH each enhanced it about 1.5-fold. Pretreatment of cells with either UFH or LMWH also enhanced the thrombin stimulation. In addition, UFH and LMWH each enhanced PGI2 production stimulated by calcium ionophore A23187, but did not affect that stimulated by arachidonic acid. From these results, it was suggested that UFH and LMWH might cause a physical change of cell membrane, which would caused an easier liberation of arachidonic acid by phospholipases.