ACTIVATION OF MITOGEN-ACTIVATED PROTEIN-KINASES BY VASCULAR ENDOTHELIAL GROWTH-FACTOR AND BASIC FIBROBLAST GROWTH-FACTOR IN CAPILLARY ENDOTHELIAL-CELLS IS INHIBITED BY THE ANTIANGIOGENIC FACTOR 16-KDA N-TERMINAL FRAGMENT OF PROLACTIN

A number of factors both stimulating and inhibiting angiogenesis have been described, In the current work, we demonstrate that the angiogeni c factor vascular endothelial growth factor (VEGF) activates mitogen-a ctivated protein kinase (MAPK) as has been previously shown for basic fibroblast growth factor. The antiangiogenic factor 16-kDa N-terminal fragment of human prolactin inhibits activation of MAPK distal to auto phosphorylation of the putative VEGF receptor, Flk-1, and phospholipas e C-gamma. These data show that activation and inhibition of MAPK may play a central role in the control of angiogenesis.