Platelet sensitivity to adenosine diphosphate and to prostacyclin in diabetic patients

We studied the platelet sensitivity to adenosine diphosphate (ADP) and to prostacyclin (PGI2) in order to clarify the mechanism of the onset or development of diabetic retinopathy. The platelet sensitivity to ADP in diabetics with simple and proliferative retinopathy was significantly increased as compared with that in diabetics without retinopathy and in controls. The platelet sensitivity to PGI2 in diabetics with simple and proliferative retinopathy was decreased significantly as compared with the normal value. There was a significant negative correlation between the platelet sensitivity to ADP and that to PGI2 in all diabetics. Since the effect of PGI2 on platelets is to inhibit its aggregation, the decreased sensitivity to PGI2 implies a tendency to accelerate platelet aggregation. The increased platelet aggregation due to the alteration of the platelet sensitivity is considered as an important factor in diabetic microangiopathy.