Intraplatelet serotonin in patients with diabetes mellitus and peripheral vascular disease

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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.