THROMBOLYTIC EFFICACY OF A MODIFIED TISSUE-TYPE PLASMINOGEN-ACTIVATOR, SUN9216, IN THE RAT MIDDLE CEREBRAL-ARTERY THROMBOSIS MODEL

We have developed a model whereby the middle cerebral artery in an experimental animal can be occluded by a photochemical reaction between rose bengal and green light. This causes endothelial injury followed by platelet adhesion, aggregation and formation of a platelet-rich thrombus at the site of the photochemical reaction. SUN9216, a modified tissue-type plasminogen activator, is a new thrombolytic agent which consists of the fibrin kringle 1 domain of plasminogen;and the two kringles, the serine protease domains of the native tissue-type plasminogen activator. The mannose glycosylation site on the kringle 1 of tissue-type plasminogen activator is modified to yield a compound with a longer half-life in the blood than native tissue-type plasminogen activator. We evaluated the thrombolytic effects of recombinant tissue-type plasminogen activator and SUN9216 in the thrombotically occluded rat middle cerebral artery. SUN9216 was administered by continuous infusion or as a single bolus injection 30 min after the middle cerebral artery had been occluded by a thrombus. Both SUN9216 and recombinant tissue-type plasminogen activator caused reopening of the middle cerebral artery by thrombolysis. The efficacy of SUN9216 was higher than that of recombinant tissue-type plasminogen activator. Further, the area of ischaemic cerebral damage caused by the middle cerebral artery occlusion was significantly (P < 0.05) reduced by SUN9216, but in this respect, recombinant tissue-type plasminogen activator was ineffective.