MORPHOLOGY AND ENZYME ACTIVITIES OF THE RETINAL CAPILLARIES IN STREPTOZOTOCIN‐DIABETIC MICE

Male lean mire belonging to the obese‐hyperglycemic strain were made diabetic by intravenous injection of streptozotocin. The retinal capillary bed freed by trypsin digestion was studied with regard to morphology and the activity of some enzymes. There was a significant increase in the ratio between the endothelial and mural cells which was interpreted as indicating mural pericyte disappearance. The activities of adenylate kinase, aspartate‐amino‐transferase and hydroxyacyl‐CoA‐dehydrogenase in the retinal vessels of the diabetic animal were significantly higher than in vessels from the control animals. No differences were found in the activities of glucose‐6‐phosphate dehydrogenase, glutathione reductase and phosphofructokinase between the two animal groups. It is suggested that these results reflect early morphological and metabolic changes of the retinal vessels, preceding the well known clinical picture of diabetic retinopathy.