Minor diurnal and activity-induced variations in daytime peripheral blood platelet counts do not have any major impact on platelet yield by platelet apheresis

Physical activity alters systemic levels of several angioregulatory cytokines that affect microvascular endothelial cells and can be assumed to influence vascular permeability. This may alter platelet release to the bone marrow microcirculation and thereby the levels of circulating platelets. We investigated effects of physical activity on angioregulatory chemokines (CXCL8, 9, 10 and 11) and peripheral blood platelet counts before and after intensive physical activity in young adults, and also compared platelet yields obtained by platelet apheresis performed in the morning and in the afternoon in 20 healthy donors. Physical activity increased serum CXCL10 levels and platelet counts but did not alter the other chemokine concentrations. In the apheresis donors, there was only a minor increase in platelet counts during the day, and the platelet yields did not differ significantly between platelet concentrates collected early in the morning and late in the afternoon. In conclusion, minor intra-individual variations in platelet counts do not seem to have major influence on platelet yields by platelet apheresis.