[Scintigraphic imaging of macrophages involved in lung vasoreflex: rat model]

At time of pathological situations, a pulmonary fixation of labelled substances injected by intravenous way is observed. This fixation would result from a phagocytosis of these substances by abnormal cells whose presence was induced in the endothelium: Pulmonary Intravascular Macrophages (PIM's). After activation by phagocytosis, these cells are able to secrete powerful vasoactive mediators capable of inducing cardiopulmonary accidents. Hepatic cholestase was induced in Wistar rats by ligation and section of common bile duct. The recruitment of PIM's was followed in vivo by phagocytosis scintigraphic imaging after labelled colloid injection. During the 35 days of evolution of the pathology, we observe a pulmonary fixation of the colloid agents which progresses up to 70% as well as a concomitant decease in the hepatic activity. Histologic examination showed numerous cells related to pulmonary capillaries' endothelium belonging to mononuclear phagocytes line and expressing an activated phenotype of monocytes. The scintigraphic and histological tests carried out enabled us to validate the model of induction of PIM's in rat by ligation of the choledoque one. The study of the vasoactive response via certain mediators can from now be approached, a Doppler technique on the pig aorta is being in the course of evaluation.