Chronic changes of the iris microvasculature of streptozotocin-induced diabetic rats using fluorescence...

This study was aimed to investigate chronic changes of the iris microvasculature in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in male Wistar-Furth rats by intravenous injection of STZ (55 mg/kg.bw). The rats were divided into control (CON) and diabetic (STZ) groups. The experiments were performed at 8, 12, 24 and 36 weeks after the injection of STZ. The iris microcirculation was visualized under a fluorescence videomicroscope. Intraluminal diameters of microvessels were measured based on the FITC-dextran images. Leukocyte adhesion to the microvascular endothelium was evaluated by counting leukocytes (labeled with rhodamine 6G). The iris blood perfusion was measured using laser Doppler flowmetry. Tissue lipid peroxidation of the eye was evaluated. The results demonstrated that the lipid peroxidation increased significantly after the injection of STZ. Both the diameters of arterioles (or precapillaries) and the iris blood perfusion decreased significantly in STZ rats, compared to the control levels. Adherent leukocytes increased significantly at 8, 12, 24 and 36 week after the injection of STZ, compared with the control levels. This indicates that the increased in oxygen-derived free radicals may be a major contributor for iris vascular endothelial dysfunction in diabetes mellitus, including leukocyte adhesion and reducing the arteriolar diameter. The present model may be useful for assessing long-term effects of therapeutic agents on diabetic retinopathy.