Dose-dependent response to IFN-gamma in muscle flap microcirculation

In this study, the authors attempted to determine the effects of intraarter ial administration of various doses of Interferon-gamma (IFN-gamma) on micr ocirculation in a rat muscle flap model. In Group 1 (control), 0.6 ml vehic le solution-PBS-BSA, in Group 2 0.6 ml IFN-gamma (25 ng/ml), in Group 3 0.6 mi IFN-gamma (50 g/ml), in Group 4 0.6 ml IFN-gamma (100 g/ml), were injec ted. The diameter of the cremaster arterioles and venules, red blood cell v elocities, the number of rolling leukocytes and lymphocytes,sticking leukoc ytes and lymphocytes, capillary perfusion, and endothelial edema index were evaluated. Deterioration of flow hemodynamics was confirmed by a significa nt decrease in flow velocity in the main artery (AI) (47 percent in Group 3 and 65 percent in Group 4). All dosages of IFN-gamma caused a statisticall y significant. decrease in rolling leukocytes, but this effect was more obv ious in the 25 ng/ml group. Injury to the vascular endothelium was confirme d by a two-fold increase in transmigrating leukocytes in the 100 ng/ml grou p. This was accompanied by 60 percent and 75 percent drops in capillary per fusion, and by 12 percent and 24 percent drops in the endothelial edema ind ex in Groups 3 and 4, respectively. The results indicate that direct intraa rterial administration of IFN-gamma in doses higher than 25 ng/ml may be to xic to muscle flaps.