Increased calcium response to ADP in blood platelets from women during ovulation compared with menstruation: cytoplasmic calcium measured with the fura-2 technique.

Blood platelets from women showed increased sensitivity to adenosine diphosphate (ADP) during ovulation compared with menstruation. The increased sensitivity was registered as an increase in cytoplasmic calcium response measured with the fluorescent indicator fura-2. Agonist dose-response studies revealed an increased maximal response, but the dose that gave half maximal response was unchanged. This indicates an increased mobility of calcium, without changed affinity to receptor(s).