BINDING OF VASCULAR ANTICOAGULANT ALPHA-(ANNEXIN-V) TO THE AORTIC INTIMA OF THE HYPERCHOLESTEROLEMIC RABBIT - AN AUTORADIOGRAPHIC STUDY

Qualitative ultrastructural autoradiography was used to study the bind ing of the vascular anticoagulant alpha (annexin V) to normal and athe rosclerotic (AS) rabbit aortic intima. Recombinant annexin V was label led with I-125 by the Iodogen method. Rabbits were fed a hypercholeste rolemic (HC) diet up to 10 months. After laparotomy and exsanguination , the aortae were perfused with dilutions of I-125-annexin V (I-AV) fo r 10-15 min, either on ice or at 22 degrees C and then perfusion-fixed with aldehydes. Fragments of the labelled aortae were used for en fac e contact autoradiography, followed by Sudan Black staining of intimal lipid. Specimens were also included in Epon and sectioned for light- and electron-microscopic autoradiography. The binding of I-AV was incr eased on the AS aortae as compared with the normal ones, with an appar ent preference for the lesioned areas. Microscopically, I-AV was found at the luminal front of aortic intima, on endothelial cells (EC), on macrophage foam cells, and on their disrupted remnants. The presence o f the AV binding sites (reportedly known to interact with high affinit y with phosphatidylserine) in the rabbit AS aortic intima, together wi th other known procoagulant conditions, may contribute to the initiati on of coagulation events into the lesioned vascular wall, and may offe r a rationale for the use of annexin V as an anticoagulant drug.