DIFFERENTIAL FORMATION OF A BIOACTIVE ANTIAGGREGATING SUBSTANCE (BAS)BY LAYERS OF THE VEIN WALL

Human umbilical veins were analyzed with and without endothelium in or der to study the ability of endothelial cells and subendothelium to re lease a bioactive anti-aggregating substance (BAS: MW > 30 kDa) indepe ndent of prostacyclin (PGI(2)), To evaluate the role of the subendothe lium, the endothelial cells were removed by rubbing on filter paper fo r 1 min, We performed a histopathological study of the vessels using h ematoxylin and eosine, and stained for elastic tissue fibers in order to confirm the presence of endothelium, The supernatant from incubated vascular rings was partially purified by Sephadex G-50 to rule out PG I(2). The void volume fractions were collected and the anti-aggregatin g activity was tested on platelet aggregation induced by arachidonic a cid, ADP, collagen and epinephrine, We observed that the activity was taking place with the use of the intact endothelium while there was no activity in the denuded vein. These observations could help to explai n the well known antithrombotic properties of vascular endothelium.