Acute hyperglycemia and acute hyperinsulinemia both decrease plasma fibrinolytic activity and increase plasminogen activator type-1 (PAI-1) in the rat.

Decreased plasma fibrinolysis may contribute to accelerated atherothrombosis in diabetes. To observe whether hyperglycemia and hyperinsulinemia, common findings in type 2 diabetes, acutely affect plasma fibrinolysis in vivo, we evaluated plasma fibrinolysis (lysis of fibrin plates, free PAI-1 activity and t-PA activity) in the rat after a hyperglycemic euinsulinemic clamp (n=8), an euglycemic hyperinsulinemic clamp (n=7) or a saline infusion (n=15). Plasma fibrinolytic activity was sharply reduced after both the hyperglycemic and hyperinsulinemic clamps as compared to the respective controls (mean lysis areas on the fibrin plate, 139 +/- 21 vs. 323 +/- 30 mm(2), p <0.001; 78 +/- 27 vs. 312 +/- 27 mm(2) p <0.001, respectively). Plasma PAM activity was greater after both hyperglycemic and hyperinsulinemic clamps as compared to saline infusion (6.6 +/-2.6 vs. 1.6 +/-0.6 IU/ml, p <0.001; 26 +/-4 vs. 1.3 +/-0.7 IU/ml, p <0.0001, respectively). Plasma t-PA activity was significantly reduced both after the hyperglycemic (0.36 +/-0.15 vs. 2.17 +/-0.18 IU/ml in controls, p <0.001) and the hyperinsulinemic (0.3 +/-0.1 vs. 2.3 +/-0.3 IU/ml in control, p <0.001) clamps. These data show that in vivo both acute hyperglycemia and acute hyperinsulinemia can decrease plasma fibrinolytic potential and that this is due to increased plasma PAI-1 and decreased free t-PA activities.