Platelet-Aggregation, Platelet Camp Levels And Thromboxane B2 Synthesis In Patients With Diabetes-Mellitus

Platelet aggregation, platelet cAMP levels and thromboxane B2 (TXB2) synthesis had been investigated in 40 diabetics (20 with microangiopathy and 20 without) and 24 normal controls. The washed platelets, but not platelet rich plasma (PRP), from the diabetics show greater sensitivity to aggregation in response to thrombin, collagen and arachidonic acid than controls (P less than 0.05). Platelets from the diabetics contain the significantly decreased cAMP levels (P less than 0.01) and synthesize the significantly greater amount of TXB2 (P less than 0.01) when induced by thrombin or collagen. Conversion of exogenously added arachidonic acid to TXB2 remained unchanged (P greater than 0.05). cAMP levels in platelets from the diabetics exhibited a significant negative linear correlation with thrombin- and collagen-induced TXB2 synthesis. There was no significant difference in platelet aggregation, platelet cAMP levels and platelet TXB2 synthesis between the diabetics with and without microangiopathy. It was suggested that in the diabetic platelets: The observed increase in platelet thromboxane A2 (TXA2) synthesis should be due to the increased activity of arachidonic acid-metabolizing system, most likely at phospholipase site; the elevated platelet TXA2 levels should inhibit platelet membrane-associated adenylate cyclase which lowered the cAMP levels in platelets; and this alternation should be the mechanism of platelet hyperaggregability, which might contribute in some way to diabetic microangiopathy.