Objective: To search for relationships between alterations in vascular and platelet function and the retinal vascular pattern in male Wistar rats with streptozocin-induced diabetes after various periods of evolution of the disease.
Numbers: Five groups of five diabetic rats were studied, the duration of diabetes being 15 days or 2, 3, 6 or 9 months; a control group comprised six nondiabetic rats. Each diabetic rat that died was replaced with a new animal, for a total of 46 animals. All deaths occurred within the first 5 days of induction of the disease.
Main outcome measures: Blood glucose level, intensity of platelet aggregation, thromboxane B2 level, aortic 6-keto-prostaglandin F1 alpha level, retinal vascular morphology, percentage of retinal area covered by vessels stained with horseradish peroxidase (HRP) in photomicrographs.
Results: Thromboxane B2 production increased with the duration of diabetes (r = 0.91, p < 0.001), and aortic 6-keto-PGF1 alpha production decreased in relation to blood glucose concentration (r = -0.95, p < 0.003). Alterations in retinal vascular pattern were related to both blood glucose and vascular prostacyclin concentrations. The retinal area covered by HRP-stained vessels was 79.3% lower in the diabetic rats than in the nondiabetic rats, and this inhibition was maintained throughout the experimental period.
Conclusions: We postulate that a decrease in prostacyclin production in association with high glucose levels plays an important role in the development of retinal vascular alterations in streptozocin-diabetic rats, although an influence of thromboxane cannot be ruled out.