The pharmacokinetics of radioiodinated streptokinase have been investigated in mice and dogs in order to further explore its potential usefulness as a radiopharmaceutical to detect thrombi and neoplasms. The purified streptokinase used in these studies showed no alteration in its physical or enzymatic properties following radioiodination. In the mouse, radioiodinated streptokinase accumulated rapidly in the liver and at 4 hr, large amounts of free iodine were detected in the plasma. The plasma clearance curve in dogs was biexponential showing that 70% of the protein bound radioactivity was cleared with a half life of 15 to 25 min while the remaining 30% was cleared with a half life of 60 to 80 min. Seventy % of the plasma radioactivity appeared as free iodine after 4 hr. No change in clearance was obtained by preloading animals with unlabeled streptokinase. Based primarily on the rapid plasma clearance, deiodination, and possible limitations of effectiveness of preloading with unlabeled streptokinase, the results of these studies are in accord with the conclusion that radioiodinated streptokinase may have restricted usefulness as a radiopharmaceutical for detecting thrombi and neoplasms. The full extent of its potential usefulness, however, awaits the provision of further in vivo and in vitro studies directed at testing a covalently modified enzyme that retains streptokinase activity but whose immunologic properties have been altered so that the enzyme is not as rapidly cleared from the plasma.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Nuclear Medicine|
|State||Published - 1975|
ASJC Scopus subject areas
- Radiological and Ultrasound Technology