Glycosaminoglycans exposed on the endothelial cell surface. Binding of heparin-like molecules derived from serum

We have analyzed the glycosaminoglycans exposed on the surface of endothelial cells cultured in vitro. The cells were labelled with [35S]sodium sulfate. Chondroitin sulfate, heparan sulfate and dermatan sulfate are the main sulfated glycosaminoglycans present on the cell surface. They are synthesized by endothelial cells. However, the electrophoretic analysis and corresponding autoradiography of the glycosaminoglycans removed from the endothelial cell surface shows the presence of heparin-like compound which is not synthesized by the cells as it is unlabelled by [35S]sodium sulfate. We show here that a proteolytic treatment of the commonly used serum for cell culturing, reveals the presence of an heparin-like anticoagulant activity. These results suggest that the endothelial cells bind endogenous heparin-like molecules present in serum.