In contrast, the VEGF chains were retained in the cells.This size heterogeneity possibly reflects differences in posttranslational processing or proteolytic degradation.The cell culture supernatants were then assayed for mitogenic activity on bovine aortic Ciclopirox endothelial cells.The conditioned media which contained homodimers of VEGF or VEGF stimulated the proliferation of BAE cells to a similar extent. Media from cells transfected with VEGF cDNA had no significant mitogenic effect.Whether VEGF protein can be as active as VEGF or VEGF in stimulating the proliferation of endothelial cells remains to be determined.Asterisks indicate the location of conserved cysteine residues that are also shared by the PDGFA and PDGFB chains.The aminoterminal sequence of the signal peptide has been confirmed by a partial sequence of a genomic DNA clone. The blot was stained using a polyclonal serum raised against a synthetic peptide of the VEGF amino terminus.Lane VEGF, lane VEGF, lane VEGF, lane untransfected COS cells.In order to compare the relative abundance of these transcripts, we performed a semiquantitative PCR analysis.DMEM supplemented with FCS and the conditioned media from untransfected COS cells or from COS cells that were transfected with the vector alone were used as a negative control.After three days, the cells were dissociated with trypsin and counted in a cytometer.In both RNA samples, VEGF transcripts were not detectable.day Pentoxifylline postnatal brain, adult brain and adult kidney were also examined.This probe contained sequences common to all three VEGF forms.The signal in the adjacent neural tissue was significantly lower.The pattern of VEGF transcript distribution in the ventricular layer of day postnatal brain was similar to the pattern in embryonic brain. In adult brain, the VEGF mRNA levels in the choroid plexus appeared slightly reduced.No specific labelling was observed in the ependyme, which forms the inner lining of the ventricle. In the newborn and adult brain, VEGF transcripts were also detected in other brain regions in which single, unidentified cells were labelled.VEGF transcripts were also observed in the meningeal layer and in the area postrema of adult brain.In vitro synthesized transcripts from a truncated V EGF cDNA were included in the reaction to serve as an internal standard and resulted in the synthesis of a bp cDNA fragment.No specific labelling was observed in blood vessels and in mesangium in the glomerulus.Glomeralar capillaries are derived from outside blood vessels. Thus, VEGF is expressed at the time of embryonic kidney angiogenesis and continues to be expressed in glomerular epithelium which is adjacent to glomerular fenestrated endothelium.VEGF transcripts were localized over clusters of cell nuclei in the labyrinth layer, most likely of the multinucleated trophoblast cells. In the labyrinth, an intimate contact between the embryonic trophoblast and maternal blood space is formed.In this region, fetal blood vessels develop which are separated by trophoblast cell layers from the maternal blood sinuses. Endothelial cells of the labyrinth are also characterized by frequent fenestrations. Discussion VEGF has important properties that are characteristic of a potential regulator of embryonic angiogenesis and of endothelial cell functions.It is a secreted growth factor whose mitogenic activity is apparently restricted to vascular endothelial cells.