Changes in sensitivity to angiotensin II in platelets.

Our study on intracellular effects of angiotensin II in human platelets showed that: (1) angiotensin II increases intracellular free calcium in platelets via a receptor-operated mechanism and this increase is dose-dependent; (2) the effect on platelet intracellular free calcium depends on the extracellular calcium concentration; (3) ACE inhibition leads to an increased sensitivity of intracellular free calcium to angiotensin II but does not alter epinephrine-induced calcium increase; (4) nifedipine reduces the susceptibility of platelet intracellular free calcium for angiotensin II.