Aspirin and prostacyclin treatment of diabetic dogs.

Spontaneously diabetic dogs were treated initially (the first 1/2 yr) with i.v. prostacyclin and oral aspirin and then for 1 yr with varying doses of aspirin alone. At this time cataracts prevented visualization of retinae, and one eye of each animal was removed for examination of the vasculature of the trypsin digested retinae. Studies of the blood during the course of treatment showed an elevation of plasma cyclic adenylic acid and marked lowering of inordinately high platelet count and platelet aggregation. Treatment was stopped and after an additional 1/2 year the animals were euthanized and the fellow eye removed for retinal study. Although just three diabetic animals survived for binocular retinal histology, there were no discernible differences in the retinal vasculature in the fellow eyes of a given animal, and in only one of these three animals were there clear signs of diabetic retinopathy. We must conclude, therefore, that in spite of relative normalization of platelet function in the parameters measured during the course of treatment, we cannot yet claim a salutary effect of treatment on the diabetic retina. Cataracts prevented us from having better information on diabetic retinae prior to treatment and a redesigned study would have to include unilateral histological retinal examination before any treatment is started to determine if, indeed, improved platelet physiology slows or reverses changes in the diabetic retina.