Displacement of fibrin-bound thrombin by r-hirudin precludes the use of 131I-r-hirudin for detecting pulmonary emboli in the rabbit
Research article published in Thrombosis and haemostasis (1994)
Abstract
Pulmonary emboli are detectable by filling defects in the pulmonary vasculature upon pulmonary angiography. Emboli derived from venous thrombi are rich in fibrin to which thrombin remains bound. Hirudin, a specific thrombin inhibitor, binds to thrombin to yield a 1:1 stoichiometric complex. We examined whether 131I-recombinant hirudin (r-hirudin) could be used to detect pulmonary emboli in rabbits. Clots were formed by re-calcifying rabbit plasma in vitro, and then injected (0.034 ml) into a femoral vein to lodge in the lungs. 131I-r-hirudin (29 +/- 4 microCi/kg) was injected intravenously but emboli could not be detected by gamma camera in real time. Post-mortem analysis of lung tissue showed that 131I-r-hirudin did not associate with emboli prepared with 125I-fibrin. Because of these findings, we used different techniques to look at the binding of hirudin to plasma clots. Clots formed in vitro were incubated with 131I-r-hirudin in the presence of equimolar amounts of 125I-albumin; specific binding of 131I-r-hirudin was not observed. Experiments with immobilized fibrin(ogen) showed that 125I-r-hirudin did not bind to and remain with fibrin-bound 131I-thrombin but did lead to the inactivation and displacement of up to 70% of bound thrombin as r-hirudin-thrombin complex; residual thrombin bound to fibrin remained active. Thus, released r-hirudin-thrombin complex is probably cleared rapidly from the region of the embolus in vivo; radioiodinated r-hirudin may not, therefore, be useful as a marker for detecting emboli.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Resumen
Displacement of fibrin-bound thrombin by r-hirudin precludes the use of 131I-r-hirudin for detecting pulmonary emboli in the rabbit.
Por qué esto importa para la hirudoterapia
Este estudio investigó si la hirudina recombinante marcada con 131I podía servir como agente de imagen para detectar embolias pulmonares en conejos, aprovechando la unión específica 1:1 de la hirudina a la trombina dentro de coágulos ricos en fibrina. La r-hirudina radiomarcada no logró localizar las embolias in vivo ni unirse específicamente a coágulos plasmáticos in vitro, debido a que inactivó y desplazó hasta el 70% de la trombina unida a fibrina como un complejo soluble r-hirudina-trombina que se eliminó rápidamente de la región del émbolo. Para el dominio de ASH, este estudio arroja luz sobre importantes propiedades farmacodinámicas de las interacciones hirudina-trombina en superficies de fibrina, relevantes para comprender cómo se comportan los anticoagulantes derivados de sanguijuelas en los sitios de los coágulos. Sin embargo, el estudio es puramente preclínico (modelo en conejo) y sus hallazgos son en realidad negativos respecto a una aplicación diagnóstica; no se involucra ninguna hirudoterapia terapéutica.
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Añadido a la biblioteca ASH: May 27, 2026 · Última actualización del sitio: 18 de junio de 2026