Further studies on the significance of circulating platelet aggregates induced by somatostatin in man.

The aim of the present study was to further evaluate the significance of circulating platelet aggregates induced by somatostatin in insulin-dependent diabetic subjects. Eight insulin-dependent diabetics and eight normals were infused with somatostatin at increasing doses (250, 500, and 750 microgram/h), each dose for 30 min. In diabetics, somatostatin induced the appearance in blood of platelet aggregates in a dose-dependent fashion, the highest level being observed with the highest dose (750 microgram/h), p less than 0.005). In normals, circulating platelet aggregates were detected only with the infusion of the highest rate of somatostatin (p less than 0.025). This effect of somatostatin was reversible, since it tended to disappear 30 min after the infusion was stopped. In six additional insulin-dependent diabetics, a previous infusion of phentolamine (0.5 mg/min) completely prevented the appearance of platelet aggregates by somatostatin. No significant variation of the aggregation response to both ADP and collagen and the platelet count was seen in both experiments. Somatostatin, as expected, reduced the basal concentration of plasma glucose, glucagon, and C-peptide in both diabetics and normals. On the basis of these results, we suggest that somatostatin has some proaggregating capacity in vivo, probably by interacting with adrenergic mechanisms.