Increased Platelet Cytosolic Free Calcium Concentration in Essential Hypertension

Cytosolic free calcium concentration Ca2was studied in platelets of hypertensive patients with the use of the fluorescent indicator Quin 2AM. Cytosolic free Ca2was significantly higher in platelets of hypertensive patients than in those of normotensive subjects (241 ± 9 versus 192 7 nmoll, n 58 and 57, respectively P< 0.001). When all 115 subjects were included, there was a significant correlation between cytosolic free Ca2and systolic or diastolic blood pressure (r 0.262, P< 0.0025 and r 0.251, P< 0.0025, respectively). Intracellular Quin 2 concentration was measured to evaluate the formaldehyde production (a product of Quin 2/AM hydrolysis which has been described as reducing the adenosine triphosphate (ATP) production). The Quin 2 concentrations in platelets of the two groups of subjects were observed to be similar (0.41 ± 0.03 versus 0.38 ± 0.03 mmoll, n 8 and 7 for hypertensives and normotensives, respectively). The effects of prostaglandin E1(PGE1), an adenylate cyclase stimulator, on cytosolic free Ca2were studied. The presence of 10-7mol/l PGE1lowered the Ca2in platelets of hypertensive patients only, suppressing the difference between the two groups.