IN-VIVO DEMONSTRATION OF INCREASED LEUKOCYTE ENTRAPMENT IN RETINAL MICROCIRCULATION OF DIABETIC RATS

PURPOSE. Leukocytes have been reported to be less deformable and more activated in diabetes. It has also been suggested that they cause micr ovascular occlusions that may cause diabetic microangiopathy. This stu dy was designed to evaluate in vivo leukocyte dynamics in the retinal microcirculation of diabetic rats. METHODS. Streptozotocin (STZ)-induc ed diabetic rats 4 weeks after diabetes induction and spontaneously di abetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats with G weeks' du ration of diabetes were used in this study. Leukocyte dynamics were ob served with acridine orange digital fluorography, using a nuclear fluo rescent dye of acridine orange and high-resolution images from a scann ing laser ophthalmoscope. RESULTS. There was no significant difference in capillary leukocyte velocity between the STZ-induced diabetic rats (1.27 +/- 0.12 mm/sec, mean +/- SD) and nondiabetic control subjects (1.38 +/- 0.07 mm/sec) or between OLETF rats (1.31 +/- 0.17 mm/sec) an d the nondiabetic controls, Long-Evans Tokushima Otsuka (LETO) rats (1 .29 +/- 0.11 mm/sec). In contrast, the density of leukocytes trapped i n the retinal microcirculation was significantly elevated in the STZ-i nduced diabetic (2.5-fold; P < 0.01) and the OLETF rats (2-fold; P < 0 .01) compared with leukocyte density in the control subjects. CONCLUSI ONS. Pharmacologically induced and spontaneously diabetic rats showed increased leukocyte entrapment in the living retina in the early stage s of diabetes. In light of the damaging potential of leukocytes, accum ulation of leukocytes in diabetic retinas from the preretinopathy stag e could cause microvascular occlusions and dysfunction, in turn causin g diabetic retinopathy.