Alteration of Platelet Shape Change Response to Vasopressin in Patients with Diabetes mellitus.

An unaltered platelet aggregatory response to vasopressin (VP) with a lower number of platelet VP-receptors have been described in patients with Diabetes mellitus. A possible explanation could be that the lost receptors are related to a cellular event different from aggregation. We have explored VP-induced platelet shape change in diabetic and healthy subjects. We confirmed that VP-induced aggregation was identical in control and diabetic subjects. On the other hand, the diabetic patients tested did not respond to VP in terms of platelet shape change, or presented reduced responses with respect to both EC(50) and maximal shape change compared to healthy subjects. In parallel, the number of VP-receptors was reduced without any alteration in their affinity. The loss of functional shape change response to VP, combined with the decrease in the number of VP-receptors occurring in diabetic patients suggests that the two abnormalities could be related. As platelet aggregation was unaltered, there may be different receptors for shape change and aggregation. The loss of the VP-induced shape change response in diabetic patients might then result from an alteration of shape change related receptors.