糖尿病合并微血管病变患者血小板聚集、血栓烷B_2生成与cAMP含量关系的初步探讨

本文对40例糖尿病患者的血小板聚集、血栓烷B_2生成和cAMP含量进行测定并探讨其与微血管病变的关系。结果表明:糖尿病患者血小板聚集增强、血栓烷B_2生成增加,血小板cAMP含量降低。上述改变在无合并微血管病变组已存在,参与微血管病变的发生和发展。血小板血栓烷B_2生成增加可能与血小板膜磷脂酶活性有关。

Correlation among Platelet Aggregation, Platelet cAMP Content and TXB_2 Synthesis in Patients with Diabetes Mellitus

Platelet aggregation, platelet cAMP content and thromboxane B2 (TXB2) synthesis have been investigated in 40 diabetics (20 with microangiopathy and 20 without) and 24 age- and sex-matched normal controls. Washed platelets, but not PRP, from diabetic subjects show greater sensitivity to aggregation in response to collagen, thrombin and arachidonic acid than controls(P<0.05). Platelets from diabetic subjects contained significantly lowered cAMP levels(P<0.01) and synthesized significantly greater amounts of TXB2(P<0.01) when induced by collagen or thrombin than platelets from control subjects. Conversion of exogenously added arachidonic acid to TXB2 was unaltered between platelets from controls and diabetic groups(P>0.05). Platelet cAMP content from diabetic groups exhibited a significant negative linear correlation with collagen- and thrombin-induced TXB2 synthesis (r= - 0.528, P<0.05; r=-0.498, P<0.05). There is no significant difference in platelet aggregation, platelet cAMP content and platelet TXB2 synthesis from between the diabetics with and without microangiopathy. However, this study suggested that platelet TXB2 synthesis in diabetic subjects did not correlate with the serum cholesterol, triglycerides, fasting blood glucose, and glycosylated hemoglobin Ar Now, it may be postulated that in the platelets of diabetic subjects: a) the observed increase in platelet TXA2 synthesis may be due to the increased activity of the thramboxane synthetase system, most likely at phospholipase site; b) the elevated platelet TXA2 levels inhibited platelet membraneassociated adenylate cyclase which lowered the cAMP levels in platelets; c) this alteration is the mechanism of platelet hyperaggregabi-lity in diabetes; d) the alteration above is before the appearance of microangiopathy, then this suggested that altered platelet function may contribute in some way to diabetic microangiopathy.