We use an experimental model of midbrain occlusion to study the safety of investigational thrombolytics for the treatment of ischemic stroke artery occlusion in the rat. Evaluation of ischemic brain tissue damage and the incidence of hemorrhagic transformation are by μCT and histology. A commercial plasminogen and plasmin concentration assay was used to determine plasma sandwich ELISA essay. The results are informative and preliminary for our purpose and show the advantage of using the ratio plasminogen/plasmin ratio to assess the safety of thrombolytics. Due to the expected higher accuracy, lower time and lower economic The main idea of the project is to use HPLC to analyse the blood plasma of rats treated with thrombolytics. Optimization of the RP-HPLC analytical method for quantitative analysis of blood plasma for the determination of plasminogen and plasmin is currently underway. It is believed that a low plasminogen/plasmin ratio indicates increased plasminemia, which is a prerequisite for the development of adverse hemorrhages in brain tissue. Conversely, an elevation in the ratio plasminogen/plasmin is indicative of sufficient plasminogen for effective safe thrombolysis.