Summary
Experimental pulmonary thrombosis was induced in rats by intravenous infusion of 0.7
M lactic acid at a rate of 1.4 ml/100 g/hr for 2 hr. As acidosis progressed, a hyper-coagulable
state developed and microthrombi were formed predominantly in the lung, but not conspicuously
in other organs. Pulmonary thrombi thus formed were composed of aggregated platelets
in the initial stage, and of fibrin in later stages. They progressively dissolved
and had completely disappeared 12 hr after cessation of the lactic acid infusion.
During the infusion of lactic acid, the following changes were observed: progressive
decreases in platelet count, fibrinogen, antiplasmin activity and fibrinolytic activity,
and progressive increase in platelet adhesiveness. Plasma clotting time decreased
to its shortest interval after one hour of the lactic acid infusion and remained at
that level during the rest of the infusion. No fibrin degradation products (FDP) were
detected.
After cessation of the lactic acid infusion, these parameters, except for fibrinolytic
activity, tended to return to normal gradually while FDP increased markedly. Fibrinolytic
activity measured by eugolobulin lysis time remained low, suggesting depletion of
vascular activator. Plasminogen level began to fall gradually 6 hr after cessation
of the lactic acid infusion.
These dynamic coagulo-fibrinolytic changes are discussed in relation to the morphological
changes of thrombi.
