Sex-related and age-related differences in platelet function in vitro: influence of hematocrit.

Even minor changes in the sodium citrate concentration of citrated plasma from young probands due to diverse hematocrit values were found to affect platelet functional activity following in vitro stimulation. There were no differences between men and women in the platelet aggregation and TXB2 production of young probands with similar hematocrit values. Platelets from elderly persons virtually failed to respond to such changes in plasma sodium citrate. Mechanisms of increased platelet activity in the elderly are discussed. It is assumed that the age-related differences are caused by a more pronounced platelet response even to lower plasma calcium levels in citrated plasma.