Intraplatelet serotonin in patients with diabetes mellitus and peripheral vascular disease

Abstract Intraplatelet serotonin (5‐HT) content was determined in 23 patients with type I (insulin‐dependent) diabetes mellitus (IDDM), 23 patients with type II (non‐insulin‐dependent) diabetes mellitus (NIDDM), 29 patients with peripheral vascular disease (PVD) and 34 age‐matched normal subjects. Intraplatelet 5‐HT content in normal subjects showed an age‐related decline (r=–0·45; P < 0·008), as has been previously demonstrated. The median 5‐HT content in platelets of the young normal subjects was 4·36 (range: 3·62–6·79) nmol 10^‐9platelets, while that in the elderly normal subjects was 3·87 (range: 2·8–6·0) nmol 10^‐9platelets and that in young+elderly subjects was 4·05 (range: 2·8–6·8) nmol 10^‐9platelets. The median intraplatelet 5‐HT content was significantly lower (P < 0·002) in IDDM patients: 3·0 (range 1·3–6·3), NIDDM patients: 2·5 (range 1·7–5·8), PVD patients: 2·42 (range 0·94–4·98) nmol 10^‐9platelets than that in all young+elderly healthy subjects. The presence of hypertension in DM patients caused a small but significant (P < 0·05) decrease in intraplatelet 5‐HT content, whilst its presence had no effect in PVD patients. In a smaller study, it was established that NIDDM and PVD patients have significantly (P < 0·002) greater plasma 5‐HT concentrations than controls. Insulin‐dependent diabetes mellitus patients had greater plasma 5‐HT concentrations but this did not achieve statistical significance despite a 66% increment in its value. We conclude that the diminished 5‐HT content in platelets and the increased plasma levels may reflect enhanced release of 5‐HT by hyperactive platelets. This increase in plasma 5‐HT may contribute to the pathogenesis of atherosclerosis and vasospasm.