PHOTOCHEMICALLY INDUCED THROMBOSIS MODEL IN RAT FEMORAL-ARTERY AND EVALUATION OF EFFECTS OF HEPARIN AND TISSUE-TYPE PLASMINOGEN-ACTIVATOR WITH USE OF THIS MODEL

We report a new and reproducible model of thrombosis in the rat femoral artery. The thrombosis is initiated by endothelial injury subsequent to photochemical reaction between systemically injected rose bengal (10 mg/kg, i.v.) and transillumination of filtered xenon lamp (wave length: 540 nm) from the outside of the vessel. The blood flow of the femoral artery, which was monitored by a pulsed doppler flow meter, was fully stopped in 348.68 +/- 36.18 sec (n = 12) after i.v. injection of rose bengal under irradiation with green light. The formation of massive thrombosis was readily evident by visual inspection. The processes of primary endothelial injury and the subsequent formation of thrombosis during this manipulation were observed by light microscopy and analysed by the scanning and transmission electron microscopy. Pretreatment with heparin (30, 100 or 300 units/kg, i.v.) 10 min before rose bengal injection dose-dependently prolonged the time required to interrupt the blood flow. The thrombolytic activity of a tissue-type plasminogen activator (tPA) was also investigated. After the establishment of stable thrombotic occlusion of the femoral artery, infusion of tPA was started from the contralateral femoral vein for 30 min at the rate of 30 or 100-mu-g/kg/min. The occluded artery was reperfused in 2 out of 10 rats and in 9 out of 12 at the lower and higher rates of tPA infusion, respectively. That heparin could prevent the arterial occlusion and that tPA could reperfuse the occluded artery are observations consistent with the histopathological ones that the primary lesion of endothelium injured photochemically activates the platelet aggregation to form platelet-rich thrombus with extensions of erythrocyte-rich lesions. This model is expected to be a useful tool for evaluating the antithrombotic and thrombolytic agents.