Reduction of platelet aggregation induced by euglycaemic insulin clamp

To examine the effect of serum insulin independent of the level of blood glucose in vivo on platelet aggregation in healthy individuals, a euglycaemic insulin clamp was applied up to 4 h. During the clamp, blood glucose at 5.0 mmol/l and insulin levels at 100 microU/ml were maintained. Blood samples were drawn before, 2 and 4 h after the start of the insulin clamp. The platelet aggregation induced by 1 mumol/l and 2 mumol/l ADP, 1 microgram/ml collagen and 2.7 mumol/l epinephrine was measured in the blood samples. Platelet aggregation induced by adenosine diphosphate, collagen and epinephrine in the 4 h sample was significantly reduced from the pre-clamp value of 8.4% to 3.9% (p less than 0.05), 26.2% to 7.0% (p less than 0.01) and 31.8% to 9.1% (p less than 0.01), respectively. On the other hand, when the same individuals were infused with physiological saline and blood glucose (4.4 mmol/l) and insulin level (10 mIU/l) were kept within normal values, there was no difference between the values of induced platelet aggregation in samples drawn before and during the insulin infusion. It was concluded that hyperinsulinaemia reduces platelet aggregation in vivo when euglycaemia was maintained.