FIBRONECTIN INHIBITION OF PLATELET THROMBUS FORMATION IN AN IN-VIVO PORCINE MODEL OF VASCULAR INJURY

Platelets adhere and aggregate in response to exposed subendothelial m atrix during vascular injury. The present study examines the effect of plasma fibronectin on platelet deposition at a site of vascular injur y in an in vivo porcine model. The internal carotid arteries in anesth etized Yorkshire pigs were bilaterally exposed and the distal half of each vessel stripped of endothelium. Following stripping, one in situ carotid artery preparation was filled with 0.5 mg/ml porcine plasma fi bronectin and the other artery filled with vehicle solution, to serve as a control. After five minutes, 6-7 x 10(8) (111)lndium-labeled auto logous platelets were infused via a femoral vein cannula, and carotid blood flow was re-established for 20 minutes. The vessel segments were excised and deposition of platelets determined. Vascular stripping in creased platelet deposition 52-fold, as compared to unstripped vessel segments. Fibronectin pretreatment did not affect platelet deposition in control vessel segments but decreased platelet deposition by 77% in stripped vessel segments. Transmission and scanning electron microsco py indicated that reduced platelet deposition in the fibronectin treat ed group was due to decreased platelet aggregation rather than decreas ed adhesion.