An Ultrastructural Study on the Early Morphologic Changes of the Retina in Streptozotocin-induced Diabetic Rats

ABSTRACT

There have been many theories for pathogenesis of diabetic retinopathy. However,no one theory can explain all of the pathogenesis. That means many factors contribute to the pathogenesis of the diabetic retinopathy. Many studies have shown the retinal changes in long-term hyperglycemia, yet relatively few in short-term hyperglycemia. To study the changes of the retinal capillary and retinal pigment epithelium in diabetic retinopathy, we measured the thickness of the basement membrane of the retinal capil-lary endothelial cells in streptozotocin-induced diabetic rats. An morphological alterations of the retinal pigment epithelium were also examined on the 2 month-old diabetic rats. The measurement was made using 0.1 mm calibrated ruler overlaying the electron micrograph with a transparent plastic sheet on which 20 radiating lines were etched exactly 18 .apart. The SPSS and Instat program were used for statistical evaluation of the data. Comparing with the control, the increase of the thickness of the endothelial basement membrane at the 2 month-old diabetic rats was statistically significant (p<0.05). Cytoplasmic alterations such as vacuolization of capillary endothelium, changes in mitochondria and increasement of capillary endothelialcytoplasm were more prominent in diabetic rats than in control rats. Basal infoldings of retinal pigment epithelium appeared to be more frequent and deeper in diabetic rats than in control rats.