Antiplatelet effects of prostacyclin and nitric oxide in patients with type I diabetes and ischemic or edematous retinopathy

The aim of this study was investigate prostacyclin and nitric oxide (NO) an d their platelet second messengers cAMP and cGMP, in patients with type I d iabetes with or without retinopathy. We compared 20 healthy volunteers and 97 patients with type I diabetes: 24 with no signs of diabetic retinopathy (DR), 43 with ischemic-proliferative DR, and 30 with edematous DR. The foll owing parameters were recorded: platelet aggregometry, nitrites/nitrates, 6 -keto-prostaglandin-F-1 alpha, and intraplatelet cAMP and cGMP Platelet agg regation was greater in patients with edematous DR. The platelets in patien ts with diabetes were more resistant to inhibition by prostaglandin E-1 or sodium nitropruside. Nitrite concentration in patients with ischemic-prolif erative DR was 80% lower than the value in healthy controls, but there was no significant difference between the control group and patients with edema tous DR. In the latter group, stimulation of neutrophils with L-arginine in creased nitrite + nitrate production by 44 + 3.6%, whereas in patients with ischemic-proliferative DR, the increase was 9.8 +/- 0.8%. We conclude that NO production is higher in patients with type I diabetes and edematous ret inopathy than in those with ischemic-proliferative retinopathy. This findin g, together with the possibly greater production of free radicals, may expl ain the greater impairment of platelet function in the former patients.