VASCULOTROPIN VEGF STIMULATES RETINAL CAPILLARY ENDOTHELIAL-CELLS THROUGH AN AUTOCRINE PATHWAY

Purpose. To determine whether bovine retinal endothelial cells (BRECs) bind, synthesize, and respond to vasculotropin-vascular endothelial g rowth factor (VAS-VEGF). Methods. Cultured BRECs were tested for their ability to bind I-125 VAS-VEGF and their response to the growth and m igration-promoting effect of VAS-VEGF. Total RNAs extracted from BRECs were reverse transcribed and amplified by polymerase chain reaction u sing VAS-VEGF primers. The translation was assessed by a Western blot analysis and a radioreceptor assay in the BREC-conditioned medium. Neu tralization with anti-VAS-VEGF antibodies ascertained the autocrine ro le of VAS-VEGF. Results. BRECs bind VAS-VEGF on two high-affinity bind ing sites (apparent K-d of 2 and 56 pM) and can proliferate and migrat e upon the addition of recombinant VAS-VEGF. Furthermore, BRECs synthe size and secrete into their own culture medium a mitogen related to VA S-VFGF as far as two factors are concerned: chromatographic behavior o n heparin-affinity columns, and cross-reactivity with recombinant VAS- VEGF to the binding to its receptors or antibodies. Neutralization of the purified conditioned medium with anti-VAS-VEGF antibodies revealed that VAS-VEGF can act on BRECs through an autocrine pathway. Conclusi ons. This is the first description of an autocrine regulation of endot helial cell growth by VAS-VEGF that could be involved in the pathogene sis of retinal neovascularization.