Platelet cytosolic free Ca2+ concentration and serotonin (5-HT) content in essential hypertension.

Cytosolic free [Ca2+] and serotonin (5-HT) content were measured in platelets from 22 untreated hypertensive patients and 16 normotensive subjects. In hypertensive patients, cytosolic free [Ca2+] was significantly higher (239 +/- 13 nmol/l versus 186 +/- 7 nmol/l, n = 22 and 16, P less than 0.01) and 5-HT content was significantly lower than those measured in cells from control subjects (3.22 +/- 0.26 versus 4.99 +/- 0.38 X 10(-7) mol/10(11) cells, n = 22 and 16, P less than 0.001). These two parameters were closely correlated (r = -0.565, n = 38, P less than 0.001). These two concomitant changes in platelet characteristics might result from a common cause, such as cell membrane alterations. As ritanserine, a specific 5-HT2 receptor antagonist, did not modify the cytosolic free [Ca2+], a higher stimulation of 5-HT2 receptors is not likely to be responsible for the enhanced free Ca2+ levels.