The stability of tissue plasminogen activator (t-PA)

Since tissue-type plasminogen activator (t-PA) derived from tissue culture and recombinant DNA procedures has been proposed for use in thrombolytic therapy in man, it is essential that the t-PA molecule should display reasonable stability in a lyophilised state to facilitate its usefulness. In this study, four laboratories compared the potencies of three preparations of t-PA following storage at 4 degrees, 20 degrees, 37 degrees and 45 degrees C, using each t-PA stored at -20 degrees C as a reference (100% activity) in each case. A pig heart extract of t-PA was the most stable, losing no activity when stored for 30 days at 37 degrees C, while two melanoma cell tissue culture extracts varied in their storage behaviour. One was quite stable at 37 degrees C (losing about 3% of its activity) while the other lost about 16%. Thus both the pig heart t-PA and one t-PA from melanoma cell culture proved suitable for the further development of reference standards for t-PA activity.