The effect of ageing on human platelet sensitivity to serotonin.

Twelve healthy young volunteers (mean age 21, range 18-27 years) and 12 elderly people (mean age 77, range 72-86 years) were tested regarding platelet aggregation induced by adrenaline, ADP and serotonin. The serum levels of thromboxane B2 (TXB2) and serum 6-keto-PGF1 alpha and the plasma level of adrenaline and cyclic AMP (cAMP) were also measured. Platelet aggregation induced by adrenaline and ADP increased significantly in the elderly compared with the young group (P less than 0.05 and P less than 0.02, respectively). There was a substantial and highly significant increase in the response of platelets from elderly people to serotonin (P less than 0.01). No alteration was observed in the serum level of TXB2 or 6-keto-PGF1 alpha. Plasma adrenaline increased in the old group, but plasma cAMP was unaffected. As serotonin is known to amplify adrenaline- and ADR-induced platelet aggregation, the considerable increase in platelet sensitivity to serotonin could be an important factor in the increased adrenaline and ADP-induced platelet aggregability of elderly people.