Functions of endothelial cells are:
1- Serve as a physical lining of heart and blood vessels to which blood cells do not normally adhere.
2- Serve as a permeability barrier for the exchange of nutrients, metabolic end products, and fluid between plasma and interstitial fluid; regulate transport of macromolecules and other substances.
3- Secrete paracrine agents that act on adjacent vascular smooth muscle cells; these include vasodilators, such as prostacyclin and nitric oxide (endothelium-derived relaxing factor, EDRF), and vasoconstrictors—notably endothelin-1.
4- Mediate angiogenesis (new capillary growth).
5- Play a central role in vascular remodeling by detecting signals and releasing paracrine agents that act on adjacent cells in the blood vessel wall.
6- Contribute to the formation and maintenance of extracellular matrix.
7- Produce growth factors in response to damage.
8- Secrete substances that regulate platelet clumping, clotting, and anticlotting.
9- Synthesize active hormones from inactive precursors.
10- Extract or degrade hormones and other mediators.
11- Secrete cytokines during immune responses.
12- Influence vascular smooth-muscle proliferation in the disease atherosclerosis.