[Circadian rhythm of platelet aggregation induced by adrenaline and collagen in man].

In five, healthy, male subjects the circadian variation of adrenaline and collagen induced platelets aggregation has been studied. Blood samples were carried out every four hours for a 24 hours period, platelets aggregation was evaluated on the P.P.P. by Elvi-Logos aggregometer adding adrenaline (1 mM/ml) or collagen (80 mg/ml). Cosinor test was used to detect circadian rhythms. A statistically significant circadian rhythm with peak in the morning has been demonstrated using both collagen or adrenaline. It is concluded that the adrenaline and collagen induced platelets aggregation "in vitro" shows a maximum of activity in the morning.