Summary
This study investigated the contribution of endogenous suppression of fibrinolysis
and increased fibrin deposition to intestinal dysfunction and injury in a rat model
of intestinal ischemia/ reperfusion (I/R), as fibrinolytic inhibition may lead to
thrombotic obstructions that compromise microcirculation and promote intestinal injury.
Circulatory fibrinolysis was enhanced by intravenous administration of recombinant
tissue plasminogen activator (rt-PA) or by inhibition of PAI-1 by administration of
MA-33H1F7. Coagulation and fibrinolysis parameters obtained from portal blood were
correlated to fibrin deposition (determined by anti-rat fibrin antibody staining),
intestinal function (glucose/water clearance) and intestinal injury (histological
evaluation by Park/Chiu score).
Enhanced circulatory fibrinolytic activity, as evidenced by increased portal plasma
plasminogen activator activity, elevated fibrin degradation products and decreased
levels of PAI-1, did not reduce mucosal fibrin deposition and microthrombosis in postischemic
intestinal tissue. Furthermore, rt-PA or anti-PAI-1 antibody administration did not
attenuate I/R-induced intestinal injury or dysfunction, as demonstrated by intestinal
histopathology scores of 4.8±0.2 and 4.7±0.3 (control I/R group 4.7±0.2) and glucose
clearances of 47±6 and 46±9 µL/min · g (control I/R group 30±8 µL/min · g) after 40
minutes of intestinal ischemia and 3 hours of reperfusion, respectively. However,
both interventions resulted in decreased levels of interleukin-6, which may indicate
fibrin-induced modulation of inflammation. Attempts to enhance the fibrinolytic activity
(either by rt-PA or by anti-PAI-1 administration), indicated by increased portal plasma
levels of released FDP, failed to decrease mucosal fibrin deposition and to attenuate
intestinal I/R injury. Based on our observations and previous reports, the contribution
of suppressed endogenous fibrinolysis to microcirculatory fibrin deposition and I/R-injury
may be of limited importance.
Keywords
Intestine - ischemia and reperfusion - fibrinolysis - plasminogen activator - plasminogen
activator inhibitor