Nonradical oxidants of the phagocyte type induce the activation of plasmatic single chain- urokinase.
Single chain- urokinase (scu-PA) is the proenzyme of the plasminogen activator urokinase (tcu-PA). In human blood scu-PA is of great stability. Activated phagocytes generate large amounts of single chain- urokinase and of reactive oxidants (chloramines and HOCl). Since these cells participate in physiologic fibrinolysis, we were interested in the interaction between plasmatic scu-PA and chloramines. The oxidants dose dependently induce the activation of plasmatic scu-PA. Optimal activation of scu-PA occurs at about 3-5 mmol/l of chloramine-T. The findings suggest a control mechanism of scu-PA stability/activity by oxidatively modifiable plasma proteins, such as alpha-2-antiplasmin. The oxidation mechanism seems to be mediated by singlet molecular oxygen, an excited oxygen species. Basing on this scu-PA/oxidant synergism a sensitive and fast functional assay of scu-PA in human plasma is presented. Plasmatic inhibitors normally interfering with functional scu-PA measurements are inactivated by addition of chloramine-T, imitating the physiological oxidants generated by activated phagocytes. The scu-PA concentration in plasma of n = 36 healthy individuals has been determined to be 5.8 +/- 1.6 ng/ml. The lower detection limit of plasma scu-PA by the procedure described is about 1.5 ng/ml of plasma. By means of this technique scu-PA concentration during thrombolytic therapy can be measured within minutes in undiluted (direct) plasma samples, allowing adjustments of the scu-PA dosage. The present study gives further credence for a role of singlet molecular oxygen, possibly a new type of locally acting hormones (autacoid), in the regulation of the fibrinolytic pathway.
Stief
T W
TW
Division of Thrombosis and Hemostasis, Univ. Hospital Virgen del Rocío, Seville, Spain.
Stief
M H
MH
Ehrenthal
W
W
Darius
H
H
Martin
E
E
D000328:Adult; D002700:Chloramines / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008297:Male; D008353:Mannitol / Q000494:pharmacology; D008875:Middle Aged; D016877:Oxidants / Q000494:pharmacology*; D010586:Phagocytes / Q000187:drug effects*; D010960:Plasminogen Activators / Q000097:blood*; D015849:Plasminogen Inactivators / Q000097:blood; D012680:Sensitivity and Specificity; D014105:Tosyl Compounds; D014568:Urokinase-Type Plasminogen Activator / Q000097:blood*
D002700:Chloramines; D016877:Oxidants; D015849:Plasminogen Inactivators; D014105:Tosyl Compounds; C016300:chloramine-T; D008353:Mannitol; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator