Endothelium-Derived Agents in Pericyte Function/ Dysfunction U. Chakravarthy* and T. A. Gardiner Queen's University and Royal Victoria Hospitals, Grosvenor Road, Belfast BT12 6BA, UK CONTENTS Abstract ...................................................................................... 511 1. The microvasculature ........................................................................ 512 1.1. Pericytes ................................................................................ 512 1.2. Retinal pericytes ........................................................................ 513 1.3. Pericyte growth and replication .......................................................... 513 1.4. Pericyte general functions ................................................................ 514 1.5. Contractile function of the pericyte ....................................................... 514 2. Endothelium derived agents .................................................................. 515 2.1. Importance to normal vascular function and health ........................................ 515 2.2. Endothelium-derived relaxants ........................................................... 515 2.3. Endothelium-derived vasoconstrictors .................................................... 516 3. Endothelium-mediated responses in pericytes .................................................. 516 3.1. Cellular and growth factor interactions ................................................... 516 3.2. Growth inhibitory properties of the endothelium and endothelium-derived factors ........... 516 3.3. Growth-promoting activities of the endothelium ........................................... 517 3.4. Endothelins and pericytes ................................................................ 517 3.5. Endothelin receptors in pericytes ......................................................... 518 3.6. Vasoactive agents and changes in pericytes morphology in vitro ............................ 519 3.7. Vasoactive agents and retinal vessel calibre in vivo ......................................... 521 4. Pericyte-derived agents and growth factors .................................................... 522 5. Vascular dysfunction: endothelium or pericyte ................................................. 522 5.1. Dysfunctional endothelium .............................................................. 522 5.2. Dysfunctional pericyte ................................................................... 523 6. Implications of functional change ............................................................. 523 7. Future directions ............................................................................ 523 Acknowledgements ............................................................................ 524 References .................................................................................... 524 Progress in Retinal and Eye Research Vol. 18, No. 4, pp. 511 to 527, 1999 # 1999 Elsevier Science Ltd. All rights reserved Printed in Great Britain 1350-9462/99/$ - see front matter PII: S1350-9462(98)00034-2 *Corresponding author.