title: Plasminogen activator inhibitor (PAI-1) in plasma and platelets.
abstract: The distribution of PAI-1 in the plasma and platelets of normal individuals and of patients with platelet abnormalities was studied. An ELISA, capable of measuring PAI-1 in plasma at 1.5 ng/ml, and a functional assay of t-PA inhibition were used to assay platelet-free plasma (PFP), platelet-rich plasma in which the platelets were lysed (PRP) and serum. The PAI-1 concentration of normal PFP was 21.0 +/- 7.2 ng/ml (mean +/- SD) and those of PRP and serum were 282.6 +/- 68.0 and 270.3 +/- 71.9 ng/ml. The concentration of PAI-1 in PRP was proportional to the platelet count with 0.67 +/- 0.18 ng/10(6) platelets. Patients with thrombocytopenia had approximately normal PAI-1 concentrations in PFP; the extremely low concentrations in serum or PRP reflected the platelet count. A patient with grey platelet syndrome showed a comparable pattern, confirming that PAI-1 occurs in the platelet alpha-granules and indicating that the plasma concentration of PAI-1 is independent of the platelet pool of PAI-1. The median inhibitory activities towards t-PA were 1.6, 8.7 and 8.3 units/ml in normal PFP, PRP and serum respectively. PAI-1 in PFP had a median specific activity (units/mg PAI-1) about 5-fold higher than platelet PAI-1. Plasma and platelets represent two distinct pools of PAI-1, both of which should be considered in studies on the relationship between circulating PAI-1 and thrombotic disease.
authors.affiliation: Department of Medicine and Therapeutics, University of Aberdeen, Scotland.
authors.forename: N A
authors.initials: NA
authors.lastname: Booth
authors.forename: A J
authors.initials: AJ
authors.lastname: Simpson
authors.forename: A
authors.initials: A
authors.lastname: Croll
authors.forename: B
authors.initials: B
authors.lastname: Bennett
authors.forename: I R
authors.initials: IR
authors.lastname: MacGregor
mesh_terms: D000328:Adult; D001791:Blood Platelet Disorders / Q000097:blood*; D001792:Blood Platelets / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000032:analysis*; D006801:Humans; D008297:Male; D015849:Plasminogen Inactivators; D013920:Thrombocythemia, Essential / Q000097:blood; D013921:Thrombocytopenia / Q000097:blood
chemical_list: D006023:Glycoproteins; D015849:Plasminogen Inactivators