Quantifying leukocyte dynamics and plugging in retinal microcirculation of streptozotosin-induced diabetic rats

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Abstract
Purpose. To determine leukocyte kinetics in the retinal micro-circulation of streptozotosin-induced diabetic rats. Methods. Rats were made diabetic with intraperitoneal injection of streptozotosin. For one month after injection, the alteration of the velocity and plugging of leukocytes were investigated using acridine orange, which stains leukocytes, and scanning laser ophthalmoscopy. Blood plasma protein levels, such as fibrinogen and a1- and a2-globulin, were also measured. Results. Throughout the observational period, mean leukocyte velocity was similar between diabetic (1.53 ± 0.45 mm/sec) and age-matched control (1.58 ± 0.23 mm/sec) rats, but the coefficient of variation of the velocity in the diabetic rats was twice as large as that in the control rats. Plugging was increased in a sigmoidal fashion and saturated for 5 weeks or later. No differences were seen in plasma protein levels between groups. Conclusions. Within one month of the hyperglycemic condition, the velocities of leukocytes in capillaries were more varied and the leukocytes were plugged time-dependently. This action occurred not because the blood fibrinogen and globulin levels were altered, but because of the leukocyte-endothelium interaction. In streptozotosin-induced diabetic rats, retinopathy usually cannot be found during the fundus examination and fluorescein angiography. In the level of the microcirculation, however, some of the disorders have already occurred.