Increased platelet, but unaltered fibrinogen, accumulation in experimental thrombi in alloxan-induced diabetic rabbits

Platelets from diabetic humans and animals have been found previously to be hypersensitive to agonists, including thrombin, in vitro but it is unclear if this hypersensitivity also occurs in vivo and leads to a greater thrombotic tendency. In the present study, the effect of diabetes was examined on thrombus formation and vessel wall responses which result from continuous intimal injury induced by indwelling aortic catheters in rabbits. Platelet and fibrin(ogen) associated with the thrombus and damaged aortae were examined. Control or alloxan-induced diabetic rabbits (9-12 months after initial treatment) were injected with 51Cr-labeled autologous platelets and 125I-labeled fibrinogen (prepared from control rabbits) before insertion of indwelling aortic catheters. The anesthetized rabbits were perfused-fixed after 20 hr or 4 days. The dry weight of thrombus that formed was determined and platelet and fibrin(ogen) accumulation in thrombi and on injured aortae were calculated from the associated 51Cr and 125I, respectively. In diabetic rabbits, more platelets accumulated in the thrombi which formed after either 20 hr or 4 days, although the weight of thrombus and net fibrin(ogen) incorporation into the thrombus were not different from corresponding control rabbits. Net platelet and fibrin(ogen) association with the injured aortae were not different between control and diabetic rabbits. It is likely that the increased platelet accumulation in arterial thrombi in diabetic rabbits which results from continuous injury to aortae is a consequence of hypersensitivity of these platelets to thrombin generated in the thrombus and at the sites of vessel injury.