Dependence of fibrinolytic activity on the concentration of free rather than total tissue-type plasminogen activator in plasma after pharmacologic administration.
To identify factors responsible for the decline of plasma tissue-type plasminogen activator (t-PA)-specific activity that we have observed after infusions of the activator and to define the potential usefulness of selected variants of t-PA in obviating them in patients with infarction, serial plasma samples from patients (n = 4) and rabbits (n = 15) given t-PA were assayed for total t-PA antigen, t-PA activity, and free as opposed to type-1 plasminogen activator inhibitor (PAI-1)--complexed t-PA. In patients, attenuation of t-PA specific activity after infusions was evident with concentrations of total t-PA antigen that were as much as sevenfold greater than pretreatment values (62 compared with 9 ng/ml). Attenuation of t-PA activity corresponded with the disappearance of free t-PA from plasma and was associated with persistence of complexes of t-PA with PAI-1. In normal rabbits (n = 4) given wild-type t-PA by bolus injection, PAI-1 activity was 4 +/- 1 arbitrary units/ml. Attenuation of t-PA activity was not evident until 60 minutes after injection at a time when total plasma t-PA antigen concentration was as low as 13 +/- 8 ng/ml. Under these conditions, plasma t-PA was composed predominantly of free t-PA. In rabbits (n = 5) given lipopolysaccharide to increase plasma PAI-1 activity to 193 +/- 84 arbitrary units/ml, the specific activity of t-PA was attenuated as early as 15 minutes after injection at a time when total t-PA antigen concentration was as high as 164 +/- 79 ng/ml. As was the case with samples from patients, attenuation was associated with the disappearance of free t-PA and the persistence of complexes of t-PA with PAI-1. A genetically engineered variant of t-PA with comparable specific activity and a comparable rate constant of association with PAI-1 but designed to persist in the circulation manifested prolonged clearance from plasma of normal rabbits (n = 3) (t1/2 = 24.6 +/- 1.6 minutes compared with an alpha phase t1/2 of 1.9 minutes for wild-type t-PA). The variant lacked the epidermal growth factor and kringle one domains and contained a duplicated kringle two domain.(ABSTRACT TRUNCATED AT 400 WORDS)
Lucore
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CL
Cardiovascular Division, Washington University, School of Medicine, St. Louis, Missouri 63110.
Fujii
S
S
Sobel
B E
BE
D000818:Animals; D005342:Fibrinolysis / Q000187:drug effects*; D006023:Glycoproteins / Q000097:blood*; D006207:Half-Life; D006801:Humans; D008070:Lipopolysaccharides / Q000493:pharmacokinetics; D009203:Myocardial Infarction / Q000188:drug therapy; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators; D011817:Rabbits; D011994:Recombinant Proteins / Q000097:blood / Q000493:pharmacokinetics / Q000627:therapeutic use; D012008:Recurrence; D010959:Tissue Plasminogen Activator / Q000097:blood* / Q000493:pharmacokinetics / Q000627:therapeutic use
D006023:Glycoproteins; D008070:Lipopolysaccharides; D015849:Plasminogen Inactivators; D011994:Recombinant Proteins; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator