Summary
High physiological concentrations of plasma vasopressin (aVP) when achieved by infusion
cause an increase in plasma factor VIII coagulant activity and shortening of the euglobulin
clot lysis time (ECLT). To investigate the effects of aVP on components of the fibrinolytic
pathway and on thrombin generation, t healthy volunteers were infused with saline
for 30 min followed by aVP for L hour and blood samples taken every 30 min for measurement
of aVR ECtf tissue-type plasminogen activator (t-PA), t-PA inhibition (tPA-I), plasminogen
activator inhibitor L (PAI-1 Ag), activated partial thromboplastin time (APTT), fibrinopeptide
A (FPA), fibrinopeptide B 15-42 (FPBß 15-42) and crosslinked fibrin breakdown products
(XL-FDP). Plasma aVP rose to a median of 75 pg/ml after 90 min and fell to 13.8 pdml
30 min later. The APTT fell from 43.5 to 35 sec (p <0.01) but there was no change
in plasma FPA or in XL-FDP. Plasminogen activator activity (106/ECLT2) increased from 25 to 736 units (p <0.01) and t-PA from 200 to 1012 mlU/ml (p <0.01).
tPA-I fell from 8.0 to 2.7 IU/ml at 90 min (p <0.05) but PAI-1 Ag remained unchanged.
Plasma FPBß 15-42 was 2.4 and 1.2 pmol/ml before infusion with aVP and showed a small
rise to 3.5 pmol/ml after 60 min (p <0.05). The results show the effects of aVP on
fibrinolysis are mediated by an increase in t-PA. In the absence of thrombin generation
the rise in t-PA was not accompanied by changes in XL-FDP.
Keywords
Vasopressin - Tissue plasminogen activator - Fibrinolysis - Fibrinopeptide A
