Human recombinant tissue type plasminogen activator and its effect on microvascular thrombosis in the rabbit.

A new potent thrombolytic agent, human tissue type plasminogen activator (t-PA), has become available for study through recombinant DNA technology. In this series of experiments, we have tested t-PA in a reliable microvascular thrombosis model previously developed in our laboratory. Its action in preventing thrombus formation and lysing fresh clot by direct local infusion and systemic infusion was tested. The results revealed that t-PA was able to keep locally infused vessels open for 4 hours and reopen them after they were allowed to clot in 100 percent of the animals tested. Those vessels exposed only to systemic levels of t-PA achieved by the same local infusion remained thrombosed and were unaffected. Laboratory studies showed no evidence of activation of the systemic lytic state or alteration in coagulation parameters. t-PA has proved to be a protein with characteristics that make it attractive for use in microvascular surgery. The results suggest that further research may lead the way toward clinical use.