Variation in cytoplasmic calcium increase in platelets as a normal response in healthy persons

Seasonal changes in cell physiology are well known. Fluctuations of mood in humans are reflected in the serotonin metabolism in platelets. The mechanisms involved remain unknown. Over four years we have studied the increase in levels of platelet calcium caused by minimal doses of the agonists adenosine 5' diphosphate (ADP) and arginine vasopressin (A8VP) using the calcium-selective fluorescent probe fura-2. We found that in blood platelets from healthy people the basal level of calcium, the amount of calcium mobilized to the cytoplasm and, for vasopressin, the rate of calcium rise, varied periodically and sufficiently to be statistically significant.