Free calcium concentration in platelets closely relates to blood pressure in normal and essentially hypertensive subjects.

Calcium has been implicated in smooth muscle contraction, arterial resistance, and the pathophysiology of essential hypertension. Using the intracellularly trapped fluorescent dye quin2 , the free calcium concentration in platelets was found to be elevated in patients with borderline (n = 8, p less than 0.01) and established essential hypertension (n = 23, p less than 0.001) when compared with normotensive subjects (n = 30). There was a close correlation between intracellular free calcium and systolic blood pressure (n = 61, r = 0.882, p less than 0.001) as well as diastolic blood pressure (n = 61, r = 0.950, p less than 0.001). The slopes of the regression lines did not differ between the groups.