Key result
Time of day is linked to 24-hour platelet rhythms featuring morning and afternoon aggregation peaks.
Why the study?
Daily variations in platelet functional parameters and density distribution may correlate with the circadian rhythmicity of myocardial infarction onset but are not fully characterized.
Observational
Platelet function and density distribution exhibit distinct circadian rhythms, which may provide mechanistic insight into the morning peak incidence of myocardial infarction.
May inform timing of platelet testing or interventions; hypothesis-generating and should not yet change practice.
Blood platelets play a critical role in the onset of myocardial infarction, which has been shown to have a circadian rhythmicity with a peak incidence in the morning. In an attempt to correlate platelet parameters with the outcome of cardiovascular diseases, we studied the daily (24-h) variation of the following platelet parameters: distribution pattern of functional heterogeneous platelet subpopulations; serotonin uptake; ketanserin binding; aggregation upon thrombin, serotonin, and ADP stimulation; and platelet count. Furthermore, we analyzed the tryptophan and serotonin concentrations in the blood samples. The percentage of less dense platelets, which represent the subpopulation with the highest preactivation, showed a rhythmicity period of 24 h and an acrophase at 21:18 h. The time course of intermediate and high density platelets was inverse to that of low density platelets. The serotonin uptake exhibited also a rhythmicity with a 24-h period. The acrophase was at 13:50 h. The aggregation curves were inverse to the ketanserin binding curves. The serotonin concentration exhibited a 12-h rhythmicity. The results obtained suggest that (a) changes in platelet activity are reflected by several parameters of platelet function that underlie daily variations; (b) the aggregation curves show a peak in the morning, with an additional peak in the afternoon; and (c) changes in the distribution pattern occur independently from variations in platelet functions like aggregation and serotonin binding.
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Opper et al. (1994) reported an observational. Time of day was evaluated on Daily variation of platelet parameters. Time of day was associated with a 24-hour rhythmicity in less dense platelets (acrophase at 21:18 h) and serotonin uptake (acrophase at 13:50 h), alongside morning and afternoon peaks in aggregation.
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