Platelet shape change abnormalities in diabetic retinopathy.

In vitro platelet aggregation has been studied in 29 normal subjects and 35 diabetic patients with retinopathy by conventional aggregating agents and by a new technique which evaluates the platelet shape change. --Plate shape change, expressed as % light transmission variation induced by the addition of ADP (10 mumol/l) in calcium-deprived platelet rich plasma, was determined. Significant differences were found between the controls (12.6 +/- 0.7%) and the 35 diabetics (15.6 +/- 1.0%, p less than 0.02) and between controls and the subgroup of patients with proliferative retinopathy (17.3 +/- 1.1%, n = 15, p less than 0.001). Platelet aggregation induced by ADP, collagen and ristocetin did not show significant differences between normal and diabetic subjects. --The shape change is the physiological early phase of platelet aggregation and is related to energy requiring mechanisms. As yet unexplored metabolic abnormalities at this stage could account for previously described platelet abnormalities in diabetes.