[Increased capillary vulnerability in diabetic retinopathy].

The retinal capillary network is isolated by Cogan and Kuwabara's method. During prolonged trypsinization the capillaries lose their endothelial cells and pericytes and are transformed into cell-free tubes consisting of basement membranes. This occurs earlier in patients with stage I or II retinopathy than in controls with normal carbohydrate metabolism and patients with stage I hypertension. Therefore, the intercellular junctions and the adhesion between endothelial cells and subendothelial basement lamella are more loosely structured in diabetics than normal subjects, and the cells do not resist the tryptic attack as well. The higher capillary vulnerability demonstrated in these experiments contributes to bleeding and exudation. Whether the local loss of cells in the microcirculation of diabetics occurs primarily in vivo or is only unmasked in vitro manifesting pre-existing cellular damage is discussed.