Blood serotonergic mechanisms in type 2 (non-insulin-dependent) diabetes mellitus.

Serotonin (5-hydroxytryptamine, 5HT) is believed to play a role in vasospasm and increased platelet aggregability that in turn could contribute to atherosclerosis. The present study was designed to evaluate a possible participation of serotonin in the development of vascular complications in diabetes mellitus. Whole blood and plasma serotonin, the platelet uptake and release of the amine and serotonin- induced platelet aggregation were studied in 32 patients with Type 2 diabetes. The patients were divided into three groups according to the presence and advancement of retinopathy. Mean levels of blood serotonin content were significantly lower in diabetic patients. The concentration of the amine in the plasma was markedly increased in diabetes. It was correlated with vascular changes of the retina. We established that platelets from diabetic patients took up less serotonin when compared to the control group. Concomitantly enhanced spontaneous release of 5HT from platelets was observed. The platelets of diabetic patients showed increased response to serotonin. There was a relation between serotonin-induced aggregation and the presence of retinopathy. These results suggest that serotonin may be involved in the pathogenesis of diabetic vasculopathy.