Blood coagulation and fibrinolysis in SART-stressed (repeated cold-stressed) rats and drug effects on the altered hemostatic parameters.

Blood coagulation and fibrinolytic activity was studied in SART (specific alternation of rhythm in temperature)-stressed animals found to exhibit thrombocytopenia and prolonged bleeding time, and drug effects on the abnormalities were evaluated. 1) SART-stressed rats revealed prolongation of activated partial thromboplastin and thrombin time, no change in prothrombin time, decreased plasma fibrinogen levels, and shortened euglobulin clot lysis time (ELT). Antithrombin III and alpha 2-plasmin inhibitor activity remained constant following stress exposure. 2) During stress, fibrinogen levels declined from day 5 and remained depressed up to day 14. Reduction in ELT developed in a similar manner to fibrinogen. 3) Decreased fibrinogen levels were prevented by consecutive doses of tranexamic acid, an antifibrinolytic, and Neurotropin, a sedative analgesic. Shortened ELT was counteracted by chronic treatment with Neurotropin and alprazolam, an anxiolytic. Single administrations of the above agents failed to affect either change. These results indicate that SART-stressed animals exhibit suppressed intrinsic coagulability and enhanced fibrinolytic activity, but normal extrinsic coagulability. Considering the previous report together with the above results, the hemostatic system under SART stress tends uniformly toward hemorrhage. Moreover, Neurotropin appears to improve and normalize hemostatic imbalance due to SART stress, a chronic form of stress.