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  • Title: Chronic hypoxic pulmonary hypertension. Is thrombin involved?
    Author: Hampl V, Archer SL, Bach R, Nelson DP, Weir EK.
    Journal: Am Rev Respir Dis; 1993 Oct; 148(4 Pt 1):1043-8. PubMed ID: 8214923.
    Abstract:
    Thrombin contracts vascular smooth muscle and stimulates its proliferation. Using a specific thrombin inhibitor, hirudin, we studied whether thrombin contributes to the pulmonary vasoconstriction and vascular proliferation that occurs in pulmonary hypertension. Hirudin was infused intravenously (0.2 mg/h/kg) by minipumps in nine rats during a 3-wk exposure to hypobaric hypoxia (HH). Vehicle (normal saline) was infused in eight hypoxic control (HC) and seven normoxic control (NC) rats. Sufficient hirudin delivery was confirmed by a failure of undiluted plasma from HH, but not from NC and HC, to clot in response to thrombin. When the plasma samples were diluted 1:10, the thrombin time was significantly prolonged in HH when compared with that in both NC and HC. Although hirudin slightly reduced mean pulmonary arterial pressure in open-chest rats, there was no significant difference between the hypoxic groups in total pulmonary resistance, right ventricle weight, morphologic remodeling of lung vessels, or the perfusion pressure-flow relationship in isolated lungs. Vasoconstrictor responses of isolated lungs to angiotensin II and acute hypoxic challenges were not affected by hirudin treatment. We conclude that hirudin, in a dose sufficient to reduce thrombin's catalytic effect on fibrinogen, does not significantly prevent the development of chronic hypoxic pulmonary hypertension.
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