Does hypertension confer a hypercoagulable state in stroke-prone spontaneously hypertensive rats?

Objective To verify whether hypertension confers a hypercoagulable state in a hypertensive animal model Design The parameters of brood coagulation were compared between stroke-pro ne spontaneously hypertensive mts (SHR-SP) and Wistar-Kyoto (WKY) rats, Eac h rat group consisted of a younger subgroup at 8-12 weeks old (n = 12) and an older subgroup at 16-20 weeks old (n = 12). Methods Prothrombin time (PT), activated partial thromboplastin time (APTT) , fluorogenic PT, fibrinogen, fibrin/fibrinogen degradation products (FDP), thrombin-anti-thrombin III complex (TAT), factor Xa activity, antithrombin III (AT-III), tissue factor pathway inhibitor (TFPI), protein C and C1 inh ibitor were measured in both rat groups, Results There was no significant difference in FDP and TAT levels between S HR-SP and WHY rats even at 16-20 weeks when SHR-SP developed severe hyperte nsive vascular lesions, Contrary to expectations, fluorogenic PT and factor Xa activity were significantly lower in SHR-SP than in WHY rats. While the re was no significant difference in AT-III, TFPI and protein C activities b etween SHR-SP and WKY rats, C1 inhibitor activity was significantly higher in SHR-SP than in WKY rats. The elevated CI inhibitor activity was inversel y correlated with the reduced factor Xa activity. Gel-filtered fractionated plasma with C1 inhibitor activity had an inhibitory effect on the purified rat factor Xa, and immunodepletion of C1 inhibitor from the fractionated p lasma attenuated the inhibitory effect. Conclusion These results suggest that SHR-SP get into a hypocoagulable stat e rather than a hypercoagulable state, and that the reduction of factor Xa activity in SHR-SP may be related to the elevation of C1 inhibitor activity , J Hypertens 2000, 18:901-909 (C) Lippincott Williams & Wilkins.