IN-VIVO STUDY OF LEUKOCYTE-ENDOTHELIUM INTERACTION IN ENDOTOXIN-INDUCED UVEITIS

Purpose. To analyze leukocyte-endothelium interaction in iris venules of living rats and to quantify changes of leukocyte dynamics in endoto xin-induced uveitis (EIU). Methods. Lewis rats received an intraperito neal injection of 100 mu g of lipopolysaccharide (LPS; Salmonella typh imurium). Using intravital fluorescence microscopy, the iris vessels w ere examined 2, 4, 6, 10, 14, 24, and 72 hours after LPS injection. A setup for intravital fluorescence microscopy of iris venules in the ra t is described. Images are recorded with a video camera and stored on S-VHS videotape for off-line analysis. For contrast enhancement, eryth rocytes and plasma were stained with fluorescein isothiocyanate (FITC) and FITC-hydroxyethylstarch, respectively, Rhodamine 6G was used for intravital staining of leukocytes, Resolution and magnification (X850) of the system facilitates observation of individual cells in the bloo dstream in real time. Leukocytes were either flowing in the center str eam, rolling along the endothelium, or firmly adherent, Image analysis provided data on microvascular leukocyte flux and leukocyte velocity. Results. The percentage of leukocytes rolling on postcapillary venula r endothelium increased significantly (P < 0.05) 4 hours after endotox in administration, as did the number of firmly adherent cells. Leukocy te-endothelium interaction reached its maximum 6 to 10 hours before an increase of inflammatory cells in the aqueous humor. The response to endotoxin was reversible, subsiding to near-normal values after 12 hou rs. Conclusions. Intravital fluorescence microscopy provides data on m icrovascular parameters, including the number of rolling and sticking leukocytes on vascular endothelium. Inflammation of the anterior uvea was characterized with regard to leukocyte recruitment from blood to t he vessel wall.