Synergism between tissue-type plasminogen activator and a genetically engineered variant lacking the finger domain, the growth factor domain and the first kringle domain.
A modified variant of human tissue-type plasminogen activator (t-PA) lacking the finger domain (F), the growth factor domain (G) and the first kringle domain (K1), has an extended plasma half-life in vivo, compared to that of t-PA. When the variant (denoted K2P) was tested in vitro for its ability to lyse human plasma clots we found that the activity was characterized by a time lag phase and a sigmoidal dose-response curve. However, an attenuation of the lag phase in vitro was observed both when K2P was mixed with t-PA in a w/w ratio of 4:1 and when K2P was allowed to lyse a clot that had been pre-exposed to t-PA i.e. submitted to a limited plasmic digestion. Dosis that in vitro caused 50% lysis within 6 h were calculated from individual dose-response curves and were for K2P, t-PA and K2P/t-PA (4:1 w/w) 540 ng/ml, 360 ng/ml and 310 ng/ml, respectively. These results indicated a synergistic effect between K2P and t-PA. However, the data from individual dose-response curves showed that the effect of the K2P/t-PA mixture never was better than that of t-PA alone, and the synergistic effect in vitro is therefore considered to be of limited use. The thrombolytic activity in vivo was evaluated in a rabbit jugular vein thrombus model. Despite the lag phase observed in vitro, K2P was approximately 3 times as effective as t-PA in vivo (bolus injection). The thrombolytic effect of K2P was further potentiated when it was administered together with a small amount of t-PA (4:1 w/w).(ABSTRACT TRUNCATED AT 250 WORDS)
Mattson
C
C
Kabi Cardiovascular, Stockholm, Sweden.
Wikström
K
K
Sterky
C
C
Pohl
G
G
D000595:Amino Acid Sequence; D000818:Animals; D004357:Drug Synergism; D005340:Fibrinogen / Q000032:analysis; D005341:Fibrinolysin / Q000032:analysis; D006133:Growth Substances / Q000235:genetics; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D015202:Protein Engineering; D011817:Rabbits; D010959:Tissue Plasminogen Activator / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D000511:alpha-Macroglobulins / Q000032:analysis
D006133:Growth Substances; D000511:alpha-Macroglobulins; C024668:plasmin-alpha(2)-macroglobulin complex; D005340:Fibrinogen; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin