Studies on α2-antiplasmin in the rat

Abstract Antibodies were raised against the plasmin- α 2 -antiplasmin complex in the rat and found monospecific against α 2 -antiplasmin after absorption. After gel filtration of normal rat serum the α 2 -antiplasmin peak (immunological assay) was observed at the same position as the antiplasmin activity (amidolytic assay), and their position in the chromatogram was similar to that of the human α 2 -antiplasmin. After in vitro activation of rat plasma and 125 I-labelled rat plasminogen with urokinase, the plasmin- α 2 -antiplasmin complex was formed very rapidly after the start of the reaction. The plasmin- α 2 -macroglobulin complex also appeared almost immediately, but the formation rate was slow. Alpha 2 -antiplasmin-depleted rat plasma had no immediate inhibitory effect on plasmin, whereas normal rat plasma inhibited plasmin considerably. These results indicate that α 2 -antiplasmin is a primary plasmin inhibitor in the rat. The coefficient of var iation of α 2 -antiplasmin in normal rats was 8.2 7. It is concluded that the rat possesses a plasmin inhibitor with essentially the same properties as human α 2 -antiplasmin. The rat would therefore seem to be a suitable animal for studies of fibrinolysis inhibition.