Prostacyclin-thromboxane balance and retinal vascular pattern in rats with experimentally induced diabetes

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.

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.

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.

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.

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.