Stimulation of endothelial cell prostacyclin release by retina-derived factors

An angiogenic extract of bovine retina as well as two purified angiogenic growth factors, acidic and basic fibroblast growth factor, stimulate vascular endothelial cell prostacyclin (PGI2) release in vitro as measured by radioimmunoassay of its stable metabolite 6-keto PGF1 alpha (6kPGF). After incubating fetal bovine aortic endothelial cells with 10% retinal extract (RE) for 24 hr, 6.5 ng of 6-kPGF/10(5) cells were released compared to 0.8 ng of 6kPGF/10(5) cells for unstimulated endothelium. Similar qualitative results were obtained using human retina-derived microvessel endothelium. PGI2 release in response to RE depended on endothelial cell density with subconfluent cultures releasing six-fold more 6kPGF compared to confluent monolayers. Thin layer radiochromatography of endothelial cell conditioned media demonstrated enhanced release of 6-kPGF, PGE2 and arachidonic acid after RE addition. Cycloheximide and actinomycin D inhibited PGI2 release but hydroxyurea had no effect. Most of the PGI2-stimulating activity of RE was adsorbed to heparin-Sepharose and eluted by 2 M NaCl. Purified acidic (10 ng/ml) and basic (1 ng/ml) fibroblast growth factors caused seven-fold and four-fold stimulation of endothelial PGI2 release, respectively. An initial event in the regression of new blood vessels following the removal of an angiogenic stimulus is the formation of intraluminal platelet aggregates. PGI2 is a potent inhibitor of platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)