opyright@ The McGraw-Hill Companies, Ine Permission required for reproduction or display TABLE 12-4 Functions of Endothelial Cells I. Serve as a physical lining that blood cells do not normally adhere to in heart and blood vessels 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 adiacent vascular and nitric oxide(endothelium-derived relaxing factor smooth muscle cells; including vasodilators-prostacycli EDRF)and vasoconstrictors--notably endothelin-l 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 Chapter 14) 10. Extract or degrade hormones and other mediators Chapters 11, 13) I 1. Secrete cytokines during immune responses( Chapter 18) 12. Influence vascular smooth-muscle proliferation in the disease atherosclerosis