THE EFFECTS OF AGE ON PLATELET INTRACELLULAR FREE CALCIUM-CONCENTRATION IN NORMOTENSIVES AND HYPERTENSIVES

We have investigated relationships between age, blood pressure and intracellular calcium concentration in platelets from normotensives and hypertensives. In normotensives, there were positive correlations between age and platelet intracellular calcium concentration (r = 0.76, P < 0.001), age and mean arterial pressure (MAP; r = 0.55, P < 0.01) and MAP and platelet intracellular calcium concentration (r = 0.45, P < 0.01). Multiple regression analysis revealed that age was the primary determinant of platelet intracellular calcium concentration in normotensives. The effect of MAP on platelet intracellular calcium concentration when adjusted for age was not significant (P = 0.73). In hypertensives, there was no significant relationship between age and platelet intracellular calcium concentration (r = 0.15, P = 0.43), age and MAP (r = 0.17, P = 0.37) or MAP and platelet intracellular calcium concentration (r = -0.27, P = 0.15). Overall, platelet intracellular calcium concentration was significantly higher in hypertensives than in age-matched normotensives (P < 0.05). Within the age groups examined, platelet intracellular calcium concentration was significantly higher only in younger hypertensives when compared with controls of a similar mean age (P < 0.001). Thus, age, in addition to hypertension, is an important determinant of platelet intracellular calcium concentration.